#!/usr/bin/env dub
/+ dub.sdl:
name "uom_quantity_rational_exponents"
targetPath "build"
+/
/**
* Units of measure — the `ℚⁿ` variant: rational exponents make `sqrt` total.
*
* Exponents are normalized rationals (CTFE `gcd` reduction, `den > 0`), so
* dimension equality is still field-wise comparison of unique normal forms:
* `sqrt(m²)` produces exponent `2/2`, which normalizes to `1/1` and is
* therefore *the same type* as a plain length. Over `ℚ` the map `d ↦ d²` is
* an automorphism, so `sqrt` applies to every grade — including `m` itself,
* yielding the first-class grade `m^(1/2)` — which is nevertheless NOT
* addable to `m` (`static assert(!__traits(compiles, ...))`). A
* pendulum-period demo shows a fractional grade appearing transiently and
* landing back in the integer lattice.
*
* Companion to docs/research/units-of-measure/theory/free-abelian-group.md
* § "`ℤⁿ` vs `ℚⁿ`: what forces the extension, what it costs" (see also
* theory/type-system-mechanisms.md § "Fractional and irrational powers").
*
* Run with: `dub run --single quantity-rational-exponents.d`
*/
module (module) uom_quantity_rational_exponentsUnits of measure — the ℚⁿ variant: rational exponents make sqrt total.
Exponents are normalized rationals (CTFE gcd reduction, den > 0), so
dimension equality is still field-wise comparison of unique normal forms:
sqrt(m²) produces exponent 2/2, which normalizes to 1/1 and is
therefore the same type as a plain length. Over ℚ the map d ↦ d² is
an automorphism, so sqrt applies to every grade — including m itself,
yielding the first-class grade m^(1/2) — which is nevertheless NOT
addable to m (static assert(!__traits(compiles, ...))). A
pendulum-period demo shows a fractional grade appearing transiently and
landing back in the integer lattice.
Companion to docs/research/units-of-measure/theory/free-abelian-group.md
§ "ℤⁿ vs ℚⁿ: what forces the extension, what it costs" (see also
theory/type-system-mechanisms.md § "Fractional and irrational powers").
Run with: dub run --single quantity-rational-exponents.d
uom_quantity_rational_exponents;
/// Euclid on non-negative operands; CTFE-friendly, no Phobos needed.
int int uom_quantity_rational_exponents.gcd(int a, int b) pure nothrow @nogc @safeEuclid on non-negative operands; CTFE-friendly, no Phobos needed.
gcd(int (parameter) int aa, int (parameter) int bb) @safe pure nothrow @nogc
in ((parameter) int aa >= 0 && (parameter) int bb >= 0)
{
while ((parameter) int bb != 0)
{
const (local variable) const(int) tt = (parameter) int aa % (parameter) int bb;
(parameter) int aa = (parameter) int bb;
(parameter) int bb = (local variable) const(int) tt;
}
return (parameter) int aa;
}
/// A rational exponent kept in unique normal form: `gcd(num, den) == 1` and
/// `den > 0`. Normalization is what makes type identity work — equal
/// exponents are bit-identical template arguments, so `2/2` and `1/1` name
/// the *same* dimension.
struct (struct) uom_quantity_rational_exponents.RationalA rational exponent kept in unique normal form: gcd(num, den) == 1 and
den > 0. Normalization is what makes type identity work — equal
exponents are bit-identical template arguments, so 2/2 and 1/1 name
the same dimension.
Rational
{
int (field) int uom_quantity_rational_exponents.Rational.numnum;
int (field) int uom_quantity_rational_exponents.Rational.denden = 1;
invariant (void uom_quantity_rational_exponents.Rational.invariant() constden > 0, "Rational must stay normalized: den > 0");
(struct) uom_quantity_rational_exponents.RationalA rational exponent kept in unique normal form: gcd(num, den) == 1 and
den > 0. Normalization is what makes type identity work — equal
exponents are bit-identical template arguments, so 2/2 and 1/1 name
the same dimension.
Rational uom_quantity_rational_exponents.Rational uom_quantity_rational_exponents.Rational.opBinary!"+"(in uom_quantity_rational_exponents.Rational rhs) const pure nothrow @nogc @safeopBinary(string op)(in (struct) uom_quantity_rational_exponents.RationalA rational exponent kept in unique normal form: gcd(num, den) == 1 and
den > 0. Normalization is what makes type identity work — equal
exponents are bit-identical template arguments, so 2/2 and 1/1 name
the same dimension.
Rational (parameter) const(uom_quantity_rational_exponents.Rational) rhsrhs) const
if (op == "+" || op == "-")
=> uom_quantity_rational_exponents.Rational uom_quantity_rational_exponents.rational(int num, int den) pure nothrow @nogc @safeBuilds the unique normal form: reduces by the gcd and keeps ``den > 0.
rational(mixin("num * rhs.den " ~ op ~ " rhs.num * den"), (field) int uom_quantity_rational_exponents.Rational.denden * (parameter) const(uom_quantity_rational_exponents.Rational) rhsrhs.(field) int uom_quantity_rational_exponents.Rational.denden);
(struct) uom_quantity_rational_exponents.RationalA rational exponent kept in unique normal form: gcd(num, den) == 1 and
den > 0. Normalization is what makes type identity work — equal
exponents are bit-identical template arguments, so 2/2 and 1/1 name
the same dimension.
Rational uom_quantity_rational_exponents.Rational uom_quantity_rational_exponents.Rational.opUnary!"-"() const pure nothrow @nogc @safeopUnary(string op : "-")() const
=> (struct) uom_quantity_rational_exponents.RationalA rational exponent kept in unique normal form: gcd(num, den) == 1 and
den > 0. Normalization is what makes type identity work — equal
exponents are bit-identical template arguments, so 2/2 and 1/1 name
the same dimension.
Rational(-(field) int uom_quantity_rational_exponents.Rational.numnum, (field) int uom_quantity_rational_exponents.Rational.denden);
/// The exact halving that `ℤⁿ` lacks: division by 2 is total over `ℚ`.
(struct) uom_quantity_rational_exponents.RationalA rational exponent kept in unique normal form: gcd(num, den) == 1 and
den > 0. Normalization is what makes type identity work — equal
exponents are bit-identical template arguments, so 2/2 and 1/1 name
the same dimension.
Rational uom_quantity_rational_exponents.Rational uom_quantity_rational_exponents.Rational.halved() const pure nothrow @nogc @safeThe exact halving that ℤⁿ lacks: division by 2 is total over ℚ.
halved() const @safe pure nothrow @nogc
=> uom_quantity_rational_exponents.Rational uom_quantity_rational_exponents.rational(int num, int den) pure nothrow @nogc @safeBuilds the unique normal form: reduces by the gcd and keeps ``den > 0.
rational((field) int uom_quantity_rational_exponents.Rational.numnum, (field) int uom_quantity_rational_exponents.Rational.denden * 2);
}
/// Builds the unique normal form: reduces by the gcd and keeps `den > 0`.
(struct) uom_quantity_rational_exponents.RationalA rational exponent kept in unique normal form: gcd(num, den) == 1 and
den > 0. Normalization is what makes type identity work — equal
exponents are bit-identical template arguments, so 2/2 and 1/1 name
the same dimension.
Rational uom_quantity_rational_exponents.Rational uom_quantity_rational_exponents.rational(int num, int den) pure nothrow @nogc @safeBuilds the unique normal form: reduces by the gcd and keeps ``den > 0.
rational(int (parameter) int numnum, int (parameter) int denden) @safe pure nothrow @nogc
in ((parameter) int denden != 0, "denominator must be non-zero")
out (r; (local variable) const(uom_quantity_rational_exponents.Rational) rr.(field) int uom_quantity_rational_exponents.Rational.denden > 0)
{
if ((parameter) int denden < 0)
{
(parameter) int numnum = -(parameter) int numnum;
(parameter) int denden = -(parameter) int denden;
}
const (local variable) const(int) gg = int uom_quantity_rational_exponents.gcd(int a, int b) pure nothrow @nogc @safeEuclid on non-negative operands; CTFE-friendly, no Phobos needed.
gcd((parameter) int numnum < 0 ? -(parameter) int numnum : (parameter) int numnum, (parameter) int denden);
return (local variable) const(int) gg == 0 ? (struct) uom_quantity_rational_exponents.RationalA rational exponent kept in unique normal form: gcd(num, den) == 1 and
den > 0. Normalization is what makes type identity work — equal
exponents are bit-identical template arguments, so 2/2 and 1/1 name
the same dimension.
Rational(0, 1) : (struct) uom_quantity_rational_exponents.RationalA rational exponent kept in unique normal form: gcd(num, den) == 1 and
den > 0. Normalization is what makes type identity work — equal
exponents are bit-identical template arguments, so 2/2 and 1/1 name
the same dimension.
Rational((parameter) int numnum / (local variable) const(int) gg, (parameter) int denden / (local variable) const(int) gg);
}
@("Rational.normalization.unique-normal-form")
@safe pure nothrow @nogc
unittest
{
assert(uom_quantity_rational_exponents.Rational uom_quantity_rational_exponents.rational(int num, int den) pure nothrow @nogc @safeBuilds the unique normal form: reduces by the gcd and keeps ``den > 0.
rational(2, 4) == (struct) uom_quantity_rational_exponents.RationalA rational exponent kept in unique normal form: gcd(num, den) == 1 and
den > 0. Normalization is what makes type identity work — equal
exponents are bit-identical template arguments, so 2/2 and 1/1 name
the same dimension.
Rational(1, 2));
assert(uom_quantity_rational_exponents.Rational uom_quantity_rational_exponents.rational(int num, int den) pure nothrow @nogc @safeBuilds the unique normal form: reduces by the gcd and keeps ``den > 0.
rational(1, -2) == (struct) uom_quantity_rational_exponents.RationalA rational exponent kept in unique normal form: gcd(num, den) == 1 and
den > 0. Normalization is what makes type identity work — equal
exponents are bit-identical template arguments, so 2/2 and 1/1 name
the same dimension.
Rational(-1, 2));
assert(uom_quantity_rational_exponents.Rational uom_quantity_rational_exponents.rational(int num, int den) pure nothrow @nogc @safeBuilds the unique normal form: reduces by the gcd and keeps ``den > 0.
rational(0, 7) == (struct) uom_quantity_rational_exponents.RationalA rational exponent kept in unique normal form: gcd(num, den) == 1 and
den > 0. Normalization is what makes type identity work — equal
exponents are bit-identical template arguments, so 2/2 and 1/1 name
the same dimension.
Rational(0, 1));
assert((struct) uom_quantity_rational_exponents.RationalA rational exponent kept in unique normal form: gcd(num, den) == 1 and
den > 0. Normalization is what makes type identity work — equal
exponents are bit-identical template arguments, so 2/2 and 1/1 name
the same dimension.
Rational(1, 2) + uom_quantity_rational_exponents.Rational uom_quantity_rational_exponents.Rational.opBinary!"+"(in uom_quantity_rational_exponents.Rational rhs) const pure nothrow @nogc @safeRational(1, 2) == (struct) uom_quantity_rational_exponents.RationalA rational exponent kept in unique normal form: gcd(num, den) == 1 and
den > 0. Normalization is what makes type identity work — equal
exponents are bit-identical template arguments, so 2/2 and 1/1 name
the same dimension.
Rational(1));
}
/// A dimension: one element of `ℚ³` over (mass, length, time), stored as
/// normalized rational exponents.
struct (struct) uom_quantity_rational_exponents.DimA dimension: one element of ℚ³ over (mass, length, time), stored as
normalized rational exponents.
Dim
{
(struct) uom_quantity_rational_exponents.RationalA rational exponent kept in unique normal form: gcd(num, den) == 1 and
den > 0. Normalization is what makes type identity work — equal
exponents are bit-identical template arguments, so 2/2 and 1/1 name
the same dimension.
Rational (field) uom_quantity_rational_exponents.Rational uom_quantity_rational_exponents.Dim.massmass;
(struct) uom_quantity_rational_exponents.RationalA rational exponent kept in unique normal form: gcd(num, den) == 1 and
den > 0. Normalization is what makes type identity work — equal
exponents are bit-identical template arguments, so 2/2 and 1/1 name
the same dimension.
Rational (field) uom_quantity_rational_exponents.Rational uom_quantity_rational_exponents.Dim.lengthlength;
(struct) uom_quantity_rational_exponents.RationalA rational exponent kept in unique normal form: gcd(num, den) == 1 and
den > 0. Normalization is what makes type identity work — equal
exponents are bit-identical template arguments, so 2/2 and 1/1 name
the same dimension.
Rational (field) uom_quantity_rational_exponents.Rational uom_quantity_rational_exponents.Dim.timetime;
}
/// The group operation, component-wise: `sign = +1` for multiplication,
/// `sign = -1` for division (the group inverse).
(struct) uom_quantity_rational_exponents.DimA dimension: one element of ℚ³ over (mass, length, time), stored as
normalized rational exponents.
Dim uom_quantity_rational_exponents.Dim uom_quantity_rational_exponents.combine(in uom_quantity_rational_exponents.Dim a, in uom_quantity_rational_exponents.Dim b, in int sign) pure nothrow @nogc @safeThe group operation, component-wise: sign` = +1` for multiplication,
sign = -1 for division (the group inverse).
combine(in (struct) uom_quantity_rational_exponents.DimA dimension: one element of ℚ³ over (mass, length, time), stored as
normalized rational exponents.
Dim (parameter) const(uom_quantity_rational_exponents.Dim) aa, in (struct) uom_quantity_rational_exponents.DimA dimension: one element of ℚ³ over (mass, length, time), stored as
normalized rational exponents.
Dim (parameter) const(uom_quantity_rational_exponents.Dim) bb, in int (parameter) const(int) signsign) @safe pure nothrow @nogc
in ((parameter) const(int) signsign == 1 || (parameter) const(int) signsign == -1)
{
(struct) uom_quantity_rational_exponents.RationalA rational exponent kept in unique normal form: gcd(num, den) == 1 and
den > 0. Normalization is what makes type identity work — equal
exponents are bit-identical template arguments, so 2/2 and 1/1 name
the same dimension.
Rational uom_quantity_rational_exponents.Rational uom_quantity_rational_exponents.combine.signed(in uom_quantity_rational_exponents.Rational r) pure nothrow @nogc @safesigned(in (struct) uom_quantity_rational_exponents.RationalA rational exponent kept in unique normal form: gcd(num, den) == 1 and
den > 0. Normalization is what makes type identity work — equal
exponents are bit-identical template arguments, so 2/2 and 1/1 name
the same dimension.
Rational (parameter) const(uom_quantity_rational_exponents.Rational) rr) => (parameter) const(int) signsign == 1 ? (parameter) const(uom_quantity_rational_exponents.Rational) rr : -(parameter) const(uom_quantity_rational_exponents.Rational) rr;
return (struct) uom_quantity_rational_exponents.DimA dimension: one element of ℚ³ over (mass, length, time), stored as
normalized rational exponents.
Dim(
mass: (parameter) const(uom_quantity_rational_exponents.Dim) aa.(field) uom_quantity_rational_exponents.Rational uom_quantity_rational_exponents.Dim.massmass + uom_quantity_rational_exponents.Rational uom_quantity_rational_exponents.Rational.opBinary!"+"(in uom_quantity_rational_exponents.Rational rhs) const pure nothrow @nogc @safesigned((parameter) const(uom_quantity_rational_exponents.Dim) bb.(field) uom_quantity_rational_exponents.Rational uom_quantity_rational_exponents.Dim.massmass),
length: (parameter) const(uom_quantity_rational_exponents.Dim) aa.(field) uom_quantity_rational_exponents.Rational uom_quantity_rational_exponents.Dim.lengthlength + uom_quantity_rational_exponents.Rational uom_quantity_rational_exponents.Rational.opBinary!"+"(in uom_quantity_rational_exponents.Rational rhs) const pure nothrow @nogc @safesigned((parameter) const(uom_quantity_rational_exponents.Dim) bb.(field) uom_quantity_rational_exponents.Rational uom_quantity_rational_exponents.Dim.lengthlength),
time: (parameter) const(uom_quantity_rational_exponents.Dim) aa.(field) uom_quantity_rational_exponents.Rational uom_quantity_rational_exponents.Dim.timetime + uom_quantity_rational_exponents.Rational uom_quantity_rational_exponents.Rational.opBinary!"+"(in uom_quantity_rational_exponents.Rational rhs) const pure nothrow @nogc @safesigned((parameter) const(uom_quantity_rational_exponents.Dim) bb.(field) uom_quantity_rational_exponents.Rational uom_quantity_rational_exponents.Dim.timetime),
);
}
/// Halves every exponent — the dimension-level image of `sqrt`, total on
/// every grade because `ℚ³` is divisible.
(struct) uom_quantity_rational_exponents.DimA dimension: one element of ℚ³ over (mass, length, time), stored as
normalized rational exponents.
Dim uom_quantity_rational_exponents.Dim uom_quantity_rational_exponents.halved(in uom_quantity_rational_exponents.Dim d) pure nothrow @nogc @safeHalves every exponent — the dimension-level image of sqrt, total on
every grade because ℚ³ is divisible.
halved(in (struct) uom_quantity_rational_exponents.DimA dimension: one element of ℚ³ over (mass, length, time), stored as
normalized rational exponents.
Dim (parameter) const(uom_quantity_rational_exponents.Dim) dd) @safe pure nothrow @nogc
=> (struct) uom_quantity_rational_exponents.DimA dimension: one element of ℚ³ over (mass, length, time), stored as
normalized rational exponents.
Dim(mass: (parameter) const(uom_quantity_rational_exponents.Dim) dd.(field) uom_quantity_rational_exponents.Rational uom_quantity_rational_exponents.Dim.massmass.uom_quantity_rational_exponents.Rational uom_quantity_rational_exponents.Rational.halved() const pure nothrow @nogc @safeThe exact halving that ℤⁿ lacks: division by 2 is total over ℚ.
halved, length: (parameter) const(uom_quantity_rational_exponents.Dim) dd.(field) uom_quantity_rational_exponents.Rational uom_quantity_rational_exponents.Dim.lengthlength.uom_quantity_rational_exponents.Rational uom_quantity_rational_exponents.Rational.halved() const pure nothrow @nogc @safeThe exact halving that ℤⁿ lacks: division by 2 is total over ℚ.
halved, time: (parameter) const(uom_quantity_rational_exponents.Dim) dd.(field) uom_quantity_rational_exponents.Rational uom_quantity_rational_exponents.Dim.timetime.uom_quantity_rational_exponents.Rational uom_quantity_rational_exponents.Rational.halved() const pure nothrow @nogc @safeThe exact halving that ℤⁿ lacks: division by 2 is total over ℚ.
halved);
@("Dim.halved.lands-on-normal-form")
@safe pure nothrow @nogc
unittest
{
// 2/1 halves to the *normalized* 1/1, not a distinct 2/2.
static assert(uom_quantity_rational_exponents.Dim uom_quantity_rational_exponents.halved(in uom_quantity_rational_exponents.Dim d) pure nothrow @nogc @safeHalves every exponent — the dimension-level image of sqrt, total on
every grade because ℚ³ is divisible.
halved((struct) uom_quantity_rational_exponents.DimA dimension: one element of ℚ³ over (mass, length, time), stored as
normalized rational exponents.
Dim(length: (struct) uom_quantity_rational_exponents.RationalA rational exponent kept in unique normal form: gcd(num, den) == 1 and
den > 0. Normalization is what makes type identity work — equal
exponents are bit-identical template arguments, so 2/2 and 1/1 name
the same dimension.
Rational(2))) == (struct) uom_quantity_rational_exponents.DimA dimension: one element of ℚ³ over (mass, length, time), stored as
normalized rational exponents.
Dim(length: (struct) uom_quantity_rational_exponents.RationalA rational exponent kept in unique normal form: gcd(num, den) == 1 and
den > 0. Normalization is what makes type identity work — equal
exponents are bit-identical template arguments, so 2/2 and 1/1 name
the same dimension.
Rational(1)));
}
/// CTFE-built unit label, e.g. `"m^(1/2)"` or `"m s^-2"`; the identity
/// element renders as `"(dimensionless)"`. GC-allocating, but only ever
/// evaluated at compile time below.
(alias) object.string = stringstring string uom_quantity_rational_exponents.unitString(in uom_quantity_rational_exponents.Dim d) pure @safeCTFE-built unit label, e.g. "m^(1/2)" or "m s^-2"; the identity
element renders as "(dimensionless)". GC-allocating, but only ever
evaluated at compile time below.
unitString(in (struct) uom_quantity_rational_exponents.DimA dimension: one element of ℚ³ over (mass, length, time), stored as
normalized rational exponents.
Dim (parameter) const(uom_quantity_rational_exponents.Dim) dd) @safe pure
{
import (package) stdstd.(module) std.convA one-stop shop for converting values from one type to another.
Category Functions Generic asOriginalType castFrom parse to toChars bitCast Strings text wtext dtext writeText writeWText writeDText hexString Numeric octal roundTo signed unsigned Exceptions ConvException ConvOverflowException
Source
std/conv.d
conv : (alias template) to = std.conv.to(T)The to template converts a value from one type _to another.
The source type is deduced and the target type must be specified, for example the
expression to!int(42.0) converts the number 42 from
double _to int. The conversion is "safe", i.e.,
it checks for overflow; to!int(4.2e10) would throw the
ConvOverflowException exception. Overflow checks are only
inserted when necessary, e.g., to!double(42) does not do
any checking because any int fits in a double.
Conversions from string _to numeric types differ from the C equivalents
atoi() and atol() by checking for overflow and not allowing whitespace.
For conversion of strings _to signed types, the grammar recognized is:
$(PRE $(I Integer):
$(I Sign UnsignedInteger)
$(I UnsignedInteger)
$(I Sign):
$(B +)
$(B -))
For conversion _to unsigned types, the grammar recognized is:
$(PRE $(I UnsignedInteger):
$(I DecimalDigit)
$(I DecimalDigit) $(I UnsignedInteger))
to;
(alias) object.string = stringstring (local variable) string resultresult;
void void uom_quantity_rational_exponents.unitString.put(in string symbol, in uom_quantity_rational_exponents.Rational exp) pure nothrow @safeput(in (alias) object.string = stringstring (parameter) const(string) symbolsymbol, in (struct) uom_quantity_rational_exponents.RationalA rational exponent kept in unique normal form: gcd(num, den) == 1 and
den > 0. Normalization is what makes type identity work — equal
exponents are bit-identical template arguments, so 2/2 and 1/1 name
the same dimension.
Rational (parameter) const(uom_quantity_rational_exponents.Rational) expexp)
{
if ((parameter) const(uom_quantity_rational_exponents.Rational) expexp.(field) int uom_quantity_rational_exponents.Rational.numnum == 0)
return;
if ((local variable) string resultresult.(field) ulong string.lengthlength > 0)
(local variable) string resultresult ~= ' ';
(local variable) string resultresult ~= (parameter) const(string) symbolsymbol;
if ((parameter) const(uom_quantity_rational_exponents.Rational) expexp == (struct) uom_quantity_rational_exponents.RationalA rational exponent kept in unique normal form: gcd(num, den) == 1 and
den > 0. Normalization is what makes type identity work — equal
exponents are bit-identical template arguments, so 2/2 and 1/1 name
the same dimension.
Rational(1))
return;
(local variable) string resultresult ~= (parameter) const(uom_quantity_rational_exponents.Rational) expexp.(field) int uom_quantity_rational_exponents.Rational.denden == 1
? "^" ~ (parameter) const(uom_quantity_rational_exponents.Rational) expexp.(field) int uom_quantity_rational_exponents.Rational.numnum.string std.conv.to!string.to!(const(int))(const(int) __param_0) pure nothrow @safeThe to template converts a value from one type to another.
The source type is deduced and the target type must be specified, for example the
expression to`!int(42.0)` converts the number 42 from
`double` to `int`. The conversion is "safe", i.e.,
it checks for overflow; to!int(4.2e10) would throw the
ConvOverflowException exception. Overflow checks are only
inserted when necessary, e.g., ``to!double(42) does not do
any checking because any int fits in a double.
Conversions from string to numeric types differ from the C equivalents
atoi() and atol() by checking for overflow and not allowing whitespace.
For conversion of strings to signed types, the grammar recognized is:
Integer:
Sign UnsignedInteger
UnsignedInteger
Sign:
+
-
For conversion to unsigned types, the grammar recognized is:
UnsignedInteger:
DecimalDigit
DecimalDigit UnsignedInteger
Examples
Converting a value to its own type (useful mostly for generic code)
simply returns its argument.
int a = 42;
int b = to!int(a);
double c = to!double(3.14); // c is double with value 3.14
Converting among numeric types is a safe way to cast them around.
Conversions from floating-point types to integral types allow loss of
precision (the fractional part of a floating-point number). The
conversion is truncating towards zero, the same way a cast would
truncate. (To round a floating point value when casting to an
integral, use roundTo.)
import std.exception : assertThrown;
int a = 420;
assert(to!long(a) == a);
assertThrown!ConvOverflowException(to!byte(a));
assert(to!int(4.2e6) == 4200000);
assertThrown!ConvOverflowException(to!uint(-3.14));
assert(to!uint(3.14) == 3);
assert(to!uint(3.99) == 3);
assert(to!int(-3.99) == -3);
When converting strings to numeric types, note that D hexadecimal and binary
literals are not handled. Neither the prefixes that indicate the base, nor the
horizontal bar used to separate groups of digits are recognized. This also
applies to the suffixes that indicate the type.
To work around this, you can specify a radix for conversions involving numbers.
auto str = to!string(42, 16);
assert(str == "2A");
auto i = to!int(str, 16);
assert(i == 42);
Conversions from integral types to floating-point types always
succeed, but might lose accuracy. The largest integers with a
predecessor representable in floating-point format are 2^24-1 for
float, 2^53-1 for double, and 2^64-1 for real (when
real is 80-bit, e.g. on Intel machines).
// 2^24 - 1, largest proper integer representable as float
int a = 16_777_215;
assert(to!int(to!float(a)) == a);
assert(to!int(to!float(-a)) == -a);
Conversion from string types to char types enforces the input
to consist of a single code point, and said code point must
fit in the target type. Otherwise, ConvException is thrown.
import std.exception : assertThrown;
assert(to!char("a") == 'a');
assertThrown(to!char("ñ")); // 'ñ' does not fit into a char
assert(to!wchar("ñ") == 'ñ');
assertThrown(to!wchar("😃")); // '😃' does not fit into a wchar
assert(to!dchar("😃") == '😃');
// Using wstring or dstring as source type does not affect the result
assert(to!char("a"w) == 'a');
assert(to!char("a"d) == 'a');
// Two code points cannot be converted to a single one
assertThrown(to!char("ab"));
Converting an array to another array type works by converting each
element in turn. Associative arrays can be converted to associative
arrays as long as keys and values can in turn be converted.
import std.string : split;
int[] a = [1, 2, 3];
auto b = to!(float[])(a);
assert(b == [1.0f, 2, 3]);
string str = "1 2 3 4 5 6";
auto numbers = to!(double[])(split(str));
assert(numbers == [1.0, 2, 3, 4, 5, 6]);
int[string] c;
c["a"] = 1;
c["b"] = 2;
auto d = to!(double[wstring])(c);
assert(d["a"w] == 1 && d["b"w] == 2);
Conversions operate transitively, meaning that they work on arrays and
associative arrays of any complexity.
This conversion works because to`!short` applies to an `int`, to!wstring
applies to a string, to`!string` applies to a `double`, and
to!(double[]) applies to an int[]. The conversion might throw an
exception because ``to!short might fail the range check.
int[string][double[int[]]] a;
auto b = to!(short[wstring][string[double[]]])(a);
Object-to-object conversions by dynamic casting throw exception when
the source is non-null and the target is null.
import std.exception : assertThrown;
// Testing object conversions
class A {}
class B : A {}
class C : A {}
A a1 = new A, a2 = new B, a3 = new C;
assert(to!B(a2) is a2);
assert(to!C(a3) is a3);
assertThrown!ConvException(to!B(a3));
Stringize conversion from all types is supported.
String to string conversion works for any two string types having
(char, wchar, dchar) character widths and any
combination of qualifiers (mutable, const, or immutable).
Converts array (other than strings) to string.
Each element is converted by calling ``to!T.
Associative array to string conversion.
Each element is converted by calling ``to!T.
Object to string conversion calls toString against the object or
returns "null" if the object is null.
Struct to string conversion calls toString against the struct if
it is defined.
For structs that do not define toString, the conversion to string
produces the list of fields.
Enumerated types are converted to strings as their symbolic names.
Boolean values are converted to "true" or "false".
char, wchar, dchar to a string type.
Unsigned or signed integers to strings.
: Convert integral value to string in radix radix.
radix must be a value from 2 to 36.
value is treated as a signed value only if radix is 10.
The characters A through Z are used to represent values 10 through 36
and their case is determined by the letterCase parameter.
All floating point types to all string types.
Pointer to string conversions convert the pointer to a size_t value.
If pointer is char*, treat it as C-style strings.
In that case, this function is @system.
See formatValue on how toString should be defined.
// Conversion representing dynamic/static array with string
long[] a = [ 1, 3, 5 ];
assert(to!string(a) == "[1, 3, 5]");
// Conversion representing associative array with string
int[string] associativeArray = ["0":1, "1":2];
assert(to!string(associativeArray) == `["0":1, "1":2]` ||
to!string(associativeArray) == `["1":2, "0":1]`);
// char* to string conversion
assert(to!string(cast(char*) null) == "");
assert(to!string("foo\0".ptr) == "foo");
// Conversion reinterpreting void array to string
auto w = "abcx"w;
const(void)[] b = w;
assert(b.length == 8);
auto c = to!(wchar[])(b);
assert(c == "abcx");
Strings can be converted to enum types. The enum member with the same name as the
input string is returned. The comparison is case-sensitive.
A ConvException is thrown if the enum does not have the specified member.
import std.exception : assertThrown;
enum E { a, b, c }
assert(to!E("a") == E.a);
assert(to!E("b") == E.b);
assertThrown!ConvException(to!E("A"));
to!(alias) object.string = stringstring
: "^(" ~ (parameter) const(uom_quantity_rational_exponents.Rational) expexp.(field) int uom_quantity_rational_exponents.Rational.numnum.string std.conv.to!string.to!(const(int))(const(int) __param_0) pure nothrow @safeThe to template converts a value from one type to another.
The source type is deduced and the target type must be specified, for example the
expression to`!int(42.0)` converts the number 42 from
`double` to `int`. The conversion is "safe", i.e.,
it checks for overflow; to!int(4.2e10) would throw the
ConvOverflowException exception. Overflow checks are only
inserted when necessary, e.g., ``to!double(42) does not do
any checking because any int fits in a double.
Conversions from string to numeric types differ from the C equivalents
atoi() and atol() by checking for overflow and not allowing whitespace.
For conversion of strings to signed types, the grammar recognized is:
Integer:
Sign UnsignedInteger
UnsignedInteger
Sign:
+
-
For conversion to unsigned types, the grammar recognized is:
UnsignedInteger:
DecimalDigit
DecimalDigit UnsignedInteger
Examples
Converting a value to its own type (useful mostly for generic code)
simply returns its argument.
int a = 42;
int b = to!int(a);
double c = to!double(3.14); // c is double with value 3.14
Converting among numeric types is a safe way to cast them around.
Conversions from floating-point types to integral types allow loss of
precision (the fractional part of a floating-point number). The
conversion is truncating towards zero, the same way a cast would
truncate. (To round a floating point value when casting to an
integral, use roundTo.)
import std.exception : assertThrown;
int a = 420;
assert(to!long(a) == a);
assertThrown!ConvOverflowException(to!byte(a));
assert(to!int(4.2e6) == 4200000);
assertThrown!ConvOverflowException(to!uint(-3.14));
assert(to!uint(3.14) == 3);
assert(to!uint(3.99) == 3);
assert(to!int(-3.99) == -3);
When converting strings to numeric types, note that D hexadecimal and binary
literals are not handled. Neither the prefixes that indicate the base, nor the
horizontal bar used to separate groups of digits are recognized. This also
applies to the suffixes that indicate the type.
To work around this, you can specify a radix for conversions involving numbers.
auto str = to!string(42, 16);
assert(str == "2A");
auto i = to!int(str, 16);
assert(i == 42);
Conversions from integral types to floating-point types always
succeed, but might lose accuracy. The largest integers with a
predecessor representable in floating-point format are 2^24-1 for
float, 2^53-1 for double, and 2^64-1 for real (when
real is 80-bit, e.g. on Intel machines).
// 2^24 - 1, largest proper integer representable as float
int a = 16_777_215;
assert(to!int(to!float(a)) == a);
assert(to!int(to!float(-a)) == -a);
Conversion from string types to char types enforces the input
to consist of a single code point, and said code point must
fit in the target type. Otherwise, ConvException is thrown.
import std.exception : assertThrown;
assert(to!char("a") == 'a');
assertThrown(to!char("ñ")); // 'ñ' does not fit into a char
assert(to!wchar("ñ") == 'ñ');
assertThrown(to!wchar("😃")); // '😃' does not fit into a wchar
assert(to!dchar("😃") == '😃');
// Using wstring or dstring as source type does not affect the result
assert(to!char("a"w) == 'a');
assert(to!char("a"d) == 'a');
// Two code points cannot be converted to a single one
assertThrown(to!char("ab"));
Converting an array to another array type works by converting each
element in turn. Associative arrays can be converted to associative
arrays as long as keys and values can in turn be converted.
import std.string : split;
int[] a = [1, 2, 3];
auto b = to!(float[])(a);
assert(b == [1.0f, 2, 3]);
string str = "1 2 3 4 5 6";
auto numbers = to!(double[])(split(str));
assert(numbers == [1.0, 2, 3, 4, 5, 6]);
int[string] c;
c["a"] = 1;
c["b"] = 2;
auto d = to!(double[wstring])(c);
assert(d["a"w] == 1 && d["b"w] == 2);
Conversions operate transitively, meaning that they work on arrays and
associative arrays of any complexity.
This conversion works because to`!short` applies to an `int`, to!wstring
applies to a string, to`!string` applies to a `double`, and
to!(double[]) applies to an int[]. The conversion might throw an
exception because ``to!short might fail the range check.
int[string][double[int[]]] a;
auto b = to!(short[wstring][string[double[]]])(a);
Object-to-object conversions by dynamic casting throw exception when
the source is non-null and the target is null.
import std.exception : assertThrown;
// Testing object conversions
class A {}
class B : A {}
class C : A {}
A a1 = new A, a2 = new B, a3 = new C;
assert(to!B(a2) is a2);
assert(to!C(a3) is a3);
assertThrown!ConvException(to!B(a3));
Stringize conversion from all types is supported.
String to string conversion works for any two string types having
(char, wchar, dchar) character widths and any
combination of qualifiers (mutable, const, or immutable).
Converts array (other than strings) to string.
Each element is converted by calling ``to!T.
Associative array to string conversion.
Each element is converted by calling ``to!T.
Object to string conversion calls toString against the object or
returns "null" if the object is null.
Struct to string conversion calls toString against the struct if
it is defined.
For structs that do not define toString, the conversion to string
produces the list of fields.
Enumerated types are converted to strings as their symbolic names.
Boolean values are converted to "true" or "false".
char, wchar, dchar to a string type.
Unsigned or signed integers to strings.
: Convert integral value to string in radix radix.
radix must be a value from 2 to 36.
value is treated as a signed value only if radix is 10.
The characters A through Z are used to represent values 10 through 36
and their case is determined by the letterCase parameter.
All floating point types to all string types.
Pointer to string conversions convert the pointer to a size_t value.
If pointer is char*, treat it as C-style strings.
In that case, this function is @system.
See formatValue on how toString should be defined.
// Conversion representing dynamic/static array with string
long[] a = [ 1, 3, 5 ];
assert(to!string(a) == "[1, 3, 5]");
// Conversion representing associative array with string
int[string] associativeArray = ["0":1, "1":2];
assert(to!string(associativeArray) == `["0":1, "1":2]` ||
to!string(associativeArray) == `["1":2, "0":1]`);
// char* to string conversion
assert(to!string(cast(char*) null) == "");
assert(to!string("foo\0".ptr) == "foo");
// Conversion reinterpreting void array to string
auto w = "abcx"w;
const(void)[] b = w;
assert(b.length == 8);
auto c = to!(wchar[])(b);
assert(c == "abcx");
Strings can be converted to enum types. The enum member with the same name as the
input string is returned. The comparison is case-sensitive.
A ConvException is thrown if the enum does not have the specified member.
import std.exception : assertThrown;
enum E { a, b, c }
assert(to!E("a") == E.a);
assert(to!E("b") == E.b);
assertThrown!ConvException(to!E("A"));
to!(alias) object.string = stringstring ~ "/" ~ (parameter) const(uom_quantity_rational_exponents.Rational) expexp.(field) int uom_quantity_rational_exponents.Rational.denden.string std.conv.to!string.to!(const(int))(const(int) __param_0) pure nothrow @safeThe to template converts a value from one type to another.
The source type is deduced and the target type must be specified, for example the
expression to`!int(42.0)` converts the number 42 from
`double` to `int`. The conversion is "safe", i.e.,
it checks for overflow; to!int(4.2e10) would throw the
ConvOverflowException exception. Overflow checks are only
inserted when necessary, e.g., ``to!double(42) does not do
any checking because any int fits in a double.
Conversions from string to numeric types differ from the C equivalents
atoi() and atol() by checking for overflow and not allowing whitespace.
For conversion of strings to signed types, the grammar recognized is:
Integer:
Sign UnsignedInteger
UnsignedInteger
Sign:
+
-
For conversion to unsigned types, the grammar recognized is:
UnsignedInteger:
DecimalDigit
DecimalDigit UnsignedInteger
Examples
Converting a value to its own type (useful mostly for generic code)
simply returns its argument.
int a = 42;
int b = to!int(a);
double c = to!double(3.14); // c is double with value 3.14
Converting among numeric types is a safe way to cast them around.
Conversions from floating-point types to integral types allow loss of
precision (the fractional part of a floating-point number). The
conversion is truncating towards zero, the same way a cast would
truncate. (To round a floating point value when casting to an
integral, use roundTo.)
import std.exception : assertThrown;
int a = 420;
assert(to!long(a) == a);
assertThrown!ConvOverflowException(to!byte(a));
assert(to!int(4.2e6) == 4200000);
assertThrown!ConvOverflowException(to!uint(-3.14));
assert(to!uint(3.14) == 3);
assert(to!uint(3.99) == 3);
assert(to!int(-3.99) == -3);
When converting strings to numeric types, note that D hexadecimal and binary
literals are not handled. Neither the prefixes that indicate the base, nor the
horizontal bar used to separate groups of digits are recognized. This also
applies to the suffixes that indicate the type.
To work around this, you can specify a radix for conversions involving numbers.
auto str = to!string(42, 16);
assert(str == "2A");
auto i = to!int(str, 16);
assert(i == 42);
Conversions from integral types to floating-point types always
succeed, but might lose accuracy. The largest integers with a
predecessor representable in floating-point format are 2^24-1 for
float, 2^53-1 for double, and 2^64-1 for real (when
real is 80-bit, e.g. on Intel machines).
// 2^24 - 1, largest proper integer representable as float
int a = 16_777_215;
assert(to!int(to!float(a)) == a);
assert(to!int(to!float(-a)) == -a);
Conversion from string types to char types enforces the input
to consist of a single code point, and said code point must
fit in the target type. Otherwise, ConvException is thrown.
import std.exception : assertThrown;
assert(to!char("a") == 'a');
assertThrown(to!char("ñ")); // 'ñ' does not fit into a char
assert(to!wchar("ñ") == 'ñ');
assertThrown(to!wchar("😃")); // '😃' does not fit into a wchar
assert(to!dchar("😃") == '😃');
// Using wstring or dstring as source type does not affect the result
assert(to!char("a"w) == 'a');
assert(to!char("a"d) == 'a');
// Two code points cannot be converted to a single one
assertThrown(to!char("ab"));
Converting an array to another array type works by converting each
element in turn. Associative arrays can be converted to associative
arrays as long as keys and values can in turn be converted.
import std.string : split;
int[] a = [1, 2, 3];
auto b = to!(float[])(a);
assert(b == [1.0f, 2, 3]);
string str = "1 2 3 4 5 6";
auto numbers = to!(double[])(split(str));
assert(numbers == [1.0, 2, 3, 4, 5, 6]);
int[string] c;
c["a"] = 1;
c["b"] = 2;
auto d = to!(double[wstring])(c);
assert(d["a"w] == 1 && d["b"w] == 2);
Conversions operate transitively, meaning that they work on arrays and
associative arrays of any complexity.
This conversion works because to`!short` applies to an `int`, to!wstring
applies to a string, to`!string` applies to a `double`, and
to!(double[]) applies to an int[]. The conversion might throw an
exception because ``to!short might fail the range check.
int[string][double[int[]]] a;
auto b = to!(short[wstring][string[double[]]])(a);
Object-to-object conversions by dynamic casting throw exception when
the source is non-null and the target is null.
import std.exception : assertThrown;
// Testing object conversions
class A {}
class B : A {}
class C : A {}
A a1 = new A, a2 = new B, a3 = new C;
assert(to!B(a2) is a2);
assert(to!C(a3) is a3);
assertThrown!ConvException(to!B(a3));
Stringize conversion from all types is supported.
String to string conversion works for any two string types having
(char, wchar, dchar) character widths and any
combination of qualifiers (mutable, const, or immutable).
Converts array (other than strings) to string.
Each element is converted by calling ``to!T.
Associative array to string conversion.
Each element is converted by calling ``to!T.
Object to string conversion calls toString against the object or
returns "null" if the object is null.
Struct to string conversion calls toString against the struct if
it is defined.
For structs that do not define toString, the conversion to string
produces the list of fields.
Enumerated types are converted to strings as their symbolic names.
Boolean values are converted to "true" or "false".
char, wchar, dchar to a string type.
Unsigned or signed integers to strings.
: Convert integral value to string in radix radix.
radix must be a value from 2 to 36.
value is treated as a signed value only if radix is 10.
The characters A through Z are used to represent values 10 through 36
and their case is determined by the letterCase parameter.
All floating point types to all string types.
Pointer to string conversions convert the pointer to a size_t value.
If pointer is char*, treat it as C-style strings.
In that case, this function is @system.
See formatValue on how toString should be defined.
// Conversion representing dynamic/static array with string
long[] a = [ 1, 3, 5 ];
assert(to!string(a) == "[1, 3, 5]");
// Conversion representing associative array with string
int[string] associativeArray = ["0":1, "1":2];
assert(to!string(associativeArray) == `["0":1, "1":2]` ||
to!string(associativeArray) == `["1":2, "0":1]`);
// char* to string conversion
assert(to!string(cast(char*) null) == "");
assert(to!string("foo\0".ptr) == "foo");
// Conversion reinterpreting void array to string
auto w = "abcx"w;
const(void)[] b = w;
assert(b.length == 8);
auto c = to!(wchar[])(b);
assert(c == "abcx");
Strings can be converted to enum types. The enum member with the same name as the
input string is returned. The comparison is case-sensitive.
A ConvException is thrown if the enum does not have the specified member.
import std.exception : assertThrown;
enum E { a, b, c }
assert(to!E("a") == E.a);
assert(to!E("b") == E.b);
assertThrown!ConvException(to!E("A"));
to!(alias) object.string = stringstring ~ ")";
}
void uom_quantity_rational_exponents.unitString.put(in string symbol, in uom_quantity_rational_exponents.Rational exp) pure nothrow @safeput("kg", (parameter) const(uom_quantity_rational_exponents.Dim) dd.(field) uom_quantity_rational_exponents.Rational uom_quantity_rational_exponents.Dim.massmass);
void uom_quantity_rational_exponents.unitString.put(in string symbol, in uom_quantity_rational_exponents.Rational exp) pure nothrow @safeput("m", (parameter) const(uom_quantity_rational_exponents.Dim) dd.(field) uom_quantity_rational_exponents.Rational uom_quantity_rational_exponents.Dim.lengthlength);
void uom_quantity_rational_exponents.unitString.put(in string symbol, in uom_quantity_rational_exponents.Rational exp) pure nothrow @safeput("s", (parameter) const(uom_quantity_rational_exponents.Dim) dd.(field) uom_quantity_rational_exponents.Rational uom_quantity_rational_exponents.Dim.timetime);
return (local variable) string resultresult.(field) ulong string.lengthlength > 0 ? (local variable) string resultresult : "(dimensionless)";
}
/// A `ℚ³`-graded quantity: one bare `double` tagged with its grade `dim`.
struct (struct) uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(0, 1), Rational(2, 1)))A ℚ³-graded quantity: one bare double tagged with its grade dim.
Quantity(Dim dim)
{
double (field) double uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(0, 1), Rational(2, 1))).valuevalue;
/// Compile-time unit label of this grade (used by `toString`).
enum (alias) object.string = stringstring (constant) string uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(0, 1), Rational(2, 1))).symbol = "s^2"Compile-time unit label of this grade (used by toString).
symbol = string uom_quantity_rational_exponents.unitString(in uom_quantity_rational_exponents.Dim d) pure @safeCTFE-built unit label, e.g. "m^(1/2)" or "m s^-2"; the identity
element renders as "(dimensionless)". GC-allocating, but only ever
evaluated at compile time below.
unitString((constant) uom_quantity_rational_exponents.Dim uom_quantity_rational_exponents.dim = Dim(Rational(0, 1), Rational(0, 1), Rational(2, 1))dim);
/// `+`/`-` exist only within a single grade: both operands share `dim`.
(struct) uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(1, 1), Rational(0, 1)))A ℚ³-graded quantity: one bare double tagged with its grade dim.
Quantity Quantity opBinary(string op)(in Quantity rhs) const+/- exist only within a single grade: both operands share dim.
opBinary(string op)(in (struct) uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(1, 1), Rational(0, 1)))A ℚ³-graded quantity: one bare double tagged with its grade dim.
Quantity (parameter) Quantity rhsrhs) const
if (op == "+" || op == "-")
=> (struct) uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(1, 1), Rational(0, 1)))Quantity(mixin("value " ~ op ~ " rhs.value"));
/// `*`/`/` are total: the result grade adds/subtracts exponent vectors.
auto auto opBinary(string op, Dim rhsDim)(in Quantity!rhsDim rhs) const*// are total: the result grade adds/subtracts exponent vectors.
opBinary(string op, Dim rhsDim)(in (constant) uom_quantity_rational_exponents.Dim uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(1, 1), Rational(0, 1))).rhsDim = Dim(Rational(0, 1), Rational(1, 1), Rational(-2, 1))Quantity!(unresolved type) rhsDimrhsDim (parameter) Quantity!rhsDim rhsrhs) const
if (op == "*" || op == "/")
=> (template instance) Quantity!(combine(dim, rhsDim, op == "*" ? 1 : -1))Quantity!(uom_quantity_rational_exponents.Dim uom_quantity_rational_exponents.combine(in uom_quantity_rational_exponents.Dim a, in uom_quantity_rational_exponents.Dim b, in int sign) pure nothrow @nogc @safeThe group operation, component-wise: sign` = +1` for multiplication,
sign = -1 for division (the group inverse).
combine((constant) uom_quantity_rational_exponents.Dim uom_quantity_rational_exponents.dim = Dim(Rational(0, 1), Rational(1, 1), Rational(0, 1))dim, (constant) uom_quantity_rational_exponents.Dim uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(1, 1), Rational(0, 1))).rhsDim = Dim(Rational(0, 1), Rational(1, 1), Rational(-2, 1))rhsDim, (constant) string uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(1, 1), Rational(0, 1))).op = "/"op == "*" ? 1 : -1))(
mixin("value " ~ op ~ " rhs.value"));
/// Scaling by a bare number is dimensionless: the grade is unchanged.
(struct) uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(0, 1), Rational(1, 1)))A ℚ³-graded quantity: one bare double tagged with its grade dim.
Quantity Quantity opBinaryRight(string op : "*")(in double k) constScaling by a bare number is dimensionless: the grade is unchanged.
opBinaryRight(string op : "*")(in double (parameter) double kk) const
=> (struct) uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(0, 1), Rational(1, 1)))Quantity((parameter) const(double) kk * (field) double uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(0, 1), Rational(1, 1))).valuevalue);
(alias) object.string = stringstring string uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(0, 1), Rational(2, 1))).toString() const pure @safetoString() const
{
import (package) stdstd.(module) std.formatThis package provides string formatting functionality using
printf style format strings.
Submodule Function Name Description package format Converts its arguments according to a format string into a string.
| package |
sformat |
Converts its arguments according to a format string into a buffer. |
| package |
FormatException |
Signals a problem while formatting. |
| write |
formattedWrite |
Converts its arguments according to a format string and writes
the result to an output range. |
| write |
formatValue |
Formats a value of any type according to a format specifier and
writes the result to an output range. |
| read |
formattedRead |
Reads an input range according to a format string and stores the read
values into its arguments. |
| read |
unformatValue |
Reads a value from the given input range and converts it according to
a format specifier. |
| spec |
FormatSpec |
A general handler for format strings. |
| spec |
singleSpec |
Helper function that returns a FormatSpec for a single format specifier. |
Limitation
This package does not support localization, but
adheres to the rounding mode of the floating point unit, if
available.
Format Strings
The functions contained in this package use format strings. A
format string describes the layout of another string for reading or
writing purposes. A format string is composed of normal text
interspersed with format specifiers. A format specifier starts
with a percentage sign '%', optionally followed by one or more
parameters and ends with a format indicator. A format
indicator may be a simple format character or a compound
indicator.
Format strings are composed according to the following grammar:
FormatString:
FormatStringItem FormatString
FormatStringItem:
Character
FormatSpecifier
FormatSpecifier:
'%' Parameters FormatIndicator
FormatIndicator:
FormatCharacter
CompoundIndicator
FormatCharacter:
see remark below
CompoundIndicator:
'(' FormatString '%)'
'(' FormatString '%|' Delimiter '%)'
Delimiter
empty
Character Delimiter
Parameters:
Position Flags Width Precision Separator
Position:
empty
Integer '$'**
*Integer* **':'** *Integer* **'$'
Integer ':' '$'**
*Flags*:
*empty*
*Flag* *Flags*
*Flag*:
**'-'**|**'+'**|**' '**|**'0'**|**'#'**|**'='**
*Width*:
*OptionalPositionalInteger*
*Precision*:
*empty*
**'.'** *OptionalPositionalInteger*
*Separator*:
*empty*
**','** *OptionalInteger*
**','** *OptionalInteger* **'?'**
*OptionalInteger*:
*empty*
*Integer*
**'*'**
*OptionalPositionalInteger*:
*OptionalInteger*
**'*'** *Integer* **'$'
Character
'%%'
AnyCharacterExceptPercent
Integer:
NonZeroDigit Digits
Digits:
empty
Digit Digits
NonZeroDigit:
'1'|'2'|'3'|'4'|'5'|'6'|'7'|'8'|'9'
Digit:
'0'|'1'|'2'|'3'|'4'|'5'|'6'|'7'|'8'|'9'
Note
FormatCharacter is unspecified. It can be any character
that has no other purpose in this grammar, but it is
recommended to assign (lower- and uppercase) letters.
Note
The Parameters of a CompoundIndicator are currently
limited to a '-' flag.
Format Indicator
The format indicator can either be a single character or an
expression surrounded by '%(' and '%)'. It specifies the
basic manner in which a value will be formatted and is the minimum
requirement to format a value.
The following characters can be used as format characters:
FormatCharacter Semantics 's' To be formatted in a human readable format. Can be used with all types. 'c' To be formatted as a character. 'd' To be formatted as a signed decimal integer. 'u' To be formatted as a decimal image of the underlying bit representation. 'b' To be formatted as a binary image of the underlying bit representation. 'o' To be formatted as an octal image of the underlying bit representation. 'x' / 'X' To be formatted as a hexadecimal image of the underlying bit representation. 'e' / 'E' To be formatted as a real number in decimal scientific notation. 'f' / 'F' To be formatted as a real number in decimal natural notation. 'g' / 'G' To be formatted as a real number in decimal short notation. Depending on the number, a scientific notation or a natural notation is used. 'a' / 'A' To be formatted as a real number in hexadecimal scientific notation. 'r' To be formatted as raw bytes. The output may not be printable and depends on endianness.
The compound indicator can be used to describe compound types
like arrays or structs in more detail. A compound type is enclosed
within '%(' and '%)'. The enclosed sub-format string is
applied to individual elements. The trailing portion of the
sub-format string following the specifier for the element is
interpreted as the delimiter, and is therefore omitted following the
last element. The '%|' specifier may be used to explicitly
indicate the start of the delimiter, so that the preceding portion of
the string will be included following the last element.
The format string inside of the compound indicator should
contain exactly one format specifier (two in case of associative
arrays), which specifies the formatting mode of the elements of the
compound type. This format specifier can be a compound
indicator itself.
Note
Inside a compound indicator, strings and characters are
escaped automatically. To avoid this behavior, use "%-("
instead of "%(".
Flags
There are several flags that affect the outcome of the formatting.
Flag Semantics '-' When the formatted result is shorter than the value given by the width parameter, the output is left justified. Without the '-' flag, the output remains right justified.
There are two exceptions where the '-' flag has a
different meaning: (1) with 'r' it denotes to use little
endian and (2) in case of a compound indicator it means that
no special handling of the members is applied. |
| '=' |
When the formatted result is shorter than the value
given by the width parameter, the output is centered.
If the central position is not possible it is moved slightly
to the right. In this case, if '-' flag is present in
addition to the '=' flag, it is moved slightly to the left. |
| '+' / *' '* |
Applies to numerical values. By default, positive numbers are not
formatted to include the + sign. With one of these two flags present,
positive numbers are preceded by a plus sign or a space.
When both flags are present, a plus sign is used.
In case of 'r', a big endian format is used. |
| '0' |
Is applied to numerical values that are printed right justified.
If the zero flag is present, the space left to the number is
filled with zeros instead of spaces. |
| '#' |
Denotes that an alternative output must be used. This depends on the type
to be formatted and the format character used. See the
sections below for more information. |
Width, Precision and Separator
The width parameter specifies the minimum width of the result.
The meaning of precision depends on the format indicator. For
integers it denotes the minimum number of digits printed, for
real numbers it denotes the number of fractional digits and for
strings and compound types it denotes the maximum number of elements
that are included in the output.
A separator is used for formatting numbers. If it is specified,
the output is divided into chunks of three digits, separated by a ','. The number of digits in a chunk can be given explicitly by
providing a number or a ''* after the ','.
In all three cases the number of digits can be replaced by a ''*. In this scenario, the next argument is used as the number of
digits. If the argument is a negative number, the precision and
separator parameters are considered unspecified. For width,
the absolute value is used and the '-' flag is set.
The separator can also be followed by a '?'. In that case,
an additional argument is used to specify the symbol that should be
used to separate the chunks.
Position
By default, the arguments are processed in the provided order. With
the position parameter it is possible to address arguments
directly. It is also possible to denote a series of arguments with
two numbers separated by ':', that are all processed in the same
way. The second number can be omitted. In that case the series ends
with the last argument.
It's also possible to use positional arguments for width, precision and separator by adding a number and a '$' after the ''*.
Types
This section describes the result of combining types with format
characters. It is organized in 2 subsections: a list of general
information regarding the formatting of types in the presence of
format characters and a table that contains details for every
available combination of type and format character.
When formatting types, the following rules apply:
If the format character is upper case, the resulting string will
be formatted using upper case letters.
The default precision for floating point numbers is 6 digits.
Rounding of floating point numbers adheres to the rounding mode
of the floating point unit, if available.
The floating point values NaN and Infinity are formatted as
nan and inf, possibly preceded by '+' or '-' sign.
Formatting reals is only supported for 64 bit reals and 80 bit reals.
All other reals are cast to double before they are formatted. This will
cause the result to be inf for very large numbers.
Characters and strings formatted with the 's' format character
inside of compound types are surrounded by single and double quotes
and unprintable characters are escaped. To avoid this, a '-'
flag can be specified for the compound specifier
(e.g. "%-(%s%)" instead of "%(%s%)" ).
Structs, unions, classes and interfaces are formatted by calling a
toString method if available.
See module std.format.write for more
details.
Only part of these combinations can be used for reading. See
module std.format.read for more
detailed information.
This table contains descriptions for every possible combination of
type and format character:
<th scope="col" width="20%">Type</th> <th scope="col" width="20%">Format Character</th> Formatted as... <td rowspan="1">null</td> 's' null
|<td rowspan="3">bool</td> 's' |
false or true |
| 'b', 'd', 'o', 'u', 'x', 'X' |
As the integrals 0 or 1 with the same format character.
Please note, that 'o' and 'x' with '#' flag
might produce unexpected results due to special handling of
the value 0. |
| 'r' |
\0 or \1 |
|<td rowspan="4">Integral</td> 's', 'd' |
A signed decimal number. The '#' flag is ignored. |
| 'b', 'o', 'u', 'x', 'X' |
An unsigned binary, decimal, octal or hexadecimal number.
In case of 'o' and 'x', the '#' flag
denotes that the number must be preceded by 0 and 0x, with
the exception of the value 0, where this does not apply. For
'b' and 'u' the '#' flag has no effect. |
| 'e', 'E', 'f', 'F', 'g', 'G', 'a', 'A' |
As a floating point value with the same specifier.
Default precision is large enough to add all digits
of the integral value.
In case of 'a' and 'A', the integral digit can be
any hexadecimal digit.
|
| 'r' |
Characters taken directly from the binary representation. |
|<td rowspan="5">Floating Point</td> 'e', 'E' |
Scientific notation: Exactly one integral digit followed by a dot
and fractional digits, followed by the exponent.
The exponent is formatted as 'e' followed by
a '+' or '-' sign, followed by at least
two digits.
When there are no fractional digits and the '#' flag
is not present, the dot is omitted. |
| 'f', 'F' |
Natural notation: Integral digits followed by a dot and
fractional digits.
When there are no fractional digits and the '#' flag
is not present, the dot is omitted.
Please note: the difference between 'f' and 'F'
is only visible for NaN and Infinity. |
| 's', 'g', 'G' |
Short notation: If the absolute value is larger than 10 ^^ precision
or smaller than 0.0001, the scientific notation is used.
If not, the natural notation is applied.
In both cases precision denotes the count of all digits, including
the integral digits. Trailing zeros (including a trailing dot) are removed.
If '#' flag is present, trailing zeros are not removed. |
| 'a', 'A' |
Hexadecimal scientific notation: 0x followed by 1
(or 0 in case of value zero or denormalized number)
followed by a dot, fractional digits in hexadecimal
notation and an exponent. The exponent is build by p,
followed by a sign and the exponent in decimal notation.
When there are no fractional digits and the '#' flag
is not present, the dot is omitted. |
| 'r' |
Characters taken directly from the binary representation. |
|<td rowspan="3">Character</td> 's', 'c' |
As the character.
Inside of a compound indicator 's' is treated differently: The
character is surrounded by single quotes and non printable
characters are escaped. This can be avoided by preceding
the compound indicator with a '-' flag
(e.g. "%-(%s%)"). |
| 'b', 'd', 'o', 'u', 'x', 'X' |
As the integral that represents the character. |
| 'r' |
Characters taken directly from the binary representation. |
|<td rowspan="3">String</td> 's' |
The sequence of characters that form the string.
Inside of a compound indicator the string is surrounded by double quotes
and non printable characters are escaped. This can be avoided
by preceding the compound indicator with a '-' flag
(e.g. "%-(%s%)"). |
| 'r' |
The sequence of characters, each formatted with 'r'. |
| compound |
As an array of characters. |
|<td rowspan="3">Array</td> 's' |
When the elements are characters, the array is formatted as
a string. In all other cases the array is surrounded by square brackets
and the elements are separated by a comma and a space. If the elements
are strings, they are surrounded by double quotes and non
printable characters are escaped. |
| 'r' |
The sequence of the elements, each formatted with 'r'. |
| compound |
The sequence of the elements, each formatted according to the specifications
given inside of the compound specifier. |
|<td rowspan="2">Associative Array</td> 's' |
As a sequence of the elements in unpredictable order. The output is
surrounded by square brackets. The elements are separated by a
comma and a space. The elements are formatted as key:value. |
| compound |
As a sequence of the elements in unpredictable order. Each element
is formatted according to the specifications given inside of the
compound specifier. The first specifier is used for formatting
the key and the second specifier is used for formatting the value.
The order can be changed with positional arguments. For example
"%(%2$s (%1$s), %)" will write the value, followed by the key in
parenthesis. |
|<td rowspan="2">Enum</td> 's' |
The name of the value. If the name is not available, the base value
is used, preceeded by a cast. |
| All, but 's' |
Enums can be formatted with all format characters that can be used
with the base value. In that case they are formatted like the base value. |
|<td rowspan="3">Input Range</td> 's' |
When the elements of the range are characters, they are written like a string.
In all other cases, the elements are enclosed by square brackets and separated
by a comma and a space. |
| 'r' |
The sequence of the elements, each formatted with 'r'. |
| compound |
The sequence of the elements, each formatted according to the specifications
given inside of the compound specifier. |
|<td rowspan="1">Struct</td> 's' |
When the struct has neither an applicable toString
nor is an input range, it is formatted as follows:
StructType(field1, field2, ...). |
|<td rowspan="1">Class</td> 's' |
When the class has neither an applicable toString
nor is an input range, it is formatted as the
fully qualified name of the class. |
|<td rowspan="1">Union</td> 's' |
When the union has neither an applicable toString
nor is an input range, it is formatted as its base name. |
|<td rowspan="2">Pointer</td> 's' |
A null pointer is formatted as 'null'. All other pointers are
formatted as hexadecimal numbers with the format character 'X'. |
| 'x', 'X' |
Formatted as a hexadecimal number. |
|<td rowspan="3">SIMD vector</td> 's' |
The array is surrounded by square brackets
and the elements are separated by a comma and a space. |
| 'r' |
The sequence of the elements, each formatted with 'r'. |
| compound |
The sequence of the elements, each formatted according to the specifications
given inside of the compound specifier. |
|<td rowspan="1">Delegate</td> 's', 'r', compound |
As the .stringof of this delegate treated as a string.
Please note: The implementation is currently buggy
and its use is discouraged. |
Source
std/format/package.d
Examples
Simple use:
// Easiest way is to use `%s` everywhere:
assert(format("I got %s %s for %s euros.", 30, "eggs", 5.27) == "I got 30 eggs for 5.27 euros.");
// Other format characters provide more control:
assert(format("I got %b %(%X%) for %f euros.", 30, "eggs", 5.27) == "I got 11110 65676773 for 5.270000 euros.");
Compound specifiers allow formatting arrays and other compound types:
/*
The trailing end of the sub-format string following the specifier for
each item is interpreted as the array delimiter, and is therefore
omitted following the last array item:
*/
assert(format("My items are %(%s %).", [1,2,3]) == "My items are 1 2 3.");
assert(format("My items are %(%s, %).", [1,2,3]) == "My items are 1, 2, 3.");
/*
The "%|" delimiter specifier may be used to indicate where the
delimiter begins, so that the portion of the format string prior to
it will be retained in the last array element:
*/
assert(format("My items are %(-%s-%|, %).", [1,2,3]) == "My items are -1-, -2-, -3-.");
/*
These compound format specifiers may be nested in the case of a
nested array argument:
*/
auto mat = [[1, 2, 3],
[4, 5, 6],
[7, 8, 9]];
assert(format("%(%(%d %) - %)", mat), "1 2 3 - 4 5 6 - 7 8 9");
assert(format("[%(%(%d %) - %)]", mat), "[1 2 3 - 4 5 6 - 7 8 9]");
assert(format("[%([%(%d %)]%| - %)]", mat), "[1 2 3] - [4 5 6] - [7 8 9]");
/*
Strings and characters are escaped automatically inside compound
format specifiers. To avoid this behavior, use "%-(" instead of "%(":
*/
assert(format("My friends are %s.", ["John", "Nancy"]) == `My friends are ["John", "Nancy"].`);
assert(format("My friends are %(%s, %).", ["John", "Nancy"]) == `My friends are "John", "Nancy".`);
assert(format("My friends are %-(%s, %).", ["John", "Nancy"]) == `My friends are John, Nancy.`);
Using parameters:
// Flags can be used to influence to outcome:
assert(format("%g != %+#g", 3.14, 3.14) == "3.14 != +3.14000");
// Width and precision help to arrange the formatted result:
assert(format(">%10.2f<", 1234.56789) == "> 1234.57<");
// Numbers can be grouped:
assert(format("%,4d", int.max) == "21,4748,3647");
// It's possible to specify the position of an argument:
assert(format("%3$s %1$s", 3, 17, 5) == "5 3");
Providing parameters as arguments:
// Width as argument
assert(format(">%*s<", 10, "abc") == "> abc<");
// Precision as argument
assert(format(">%.*f<", 5, 123.2) == ">123.20000<");
// Grouping as argument
assert(format("%,*d", 1, int.max) == "2,1,4,7,4,8,3,6,4,7");
// Grouping separator as argument
assert(format("%,3?d", '_', int.max) == "2_147_483_647");
// All at once
assert(format("%*.*,*?d", 20, 15, 6, '/', int.max) == " 000/002147/483647");
format : (alias template) format = std.format.format(Char, Args...)(in Char[] fmt, Args args) if (isSomeChar!Char)Converts its arguments according to a format string into a string.
The second version of format takes the format string as template
argument. In this case, it is checked for consistency at
compile-time and produces slightly faster code, because the length of
the output buffer can be estimated in advance.
Params:
fmt = a $(MREF_ALTTEXT format string, std,format)
args = a variadic list of arguments to be formatted
Char = character type of fmt
Args = a variadic list of types of the arguments
Returns:
The formatted string.
Throws:
A $(LREF FormatException) if formatting did not succeed.
See_Also:
$(LREF sformat) for a variant, that tries to avoid garbage collection.
format;
return string std.format.format!("%.6g %s", const(double), string)(const(double) __param_0, string __param_1) pure @safeExamples
The format string can be checked at compile-time:
auto s = format!"%s is %s"("Pi", 3.14);
assert(s == "Pi is 3.14");
// This line doesn't compile, because 3.14 cannot be formatted with %d:
// s = format!"%s is %d"("Pi", 3.14);
format!"%.6g %s"((field) double uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(0, 1), Rational(2, 1))).valuevalue, (constant) string uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(0, 1), Rational(2, 1))).symbol = "s^2"Compile-time unit label of this grade (used by toString).
symbol);
}
}
/// `sqrt` over `ℚ³`: total on every grade — every exponent is exactly halved.
/// (In `ℤⁿ` this is typable only at even exponent vectors: Kennedy's
/// `sqrt : real d² → real d`.)
auto uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(0, 1), Rational(1, 1))) uom_quantity_rational_exponents.sqrt!(Dim(Rational(0, 1), Rational(0, 1), Rational(2, 1)))(in uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(0, 1), Rational(2, 1))) q) pure nothrow @nogc @safesqrt over ℚ³: total on every grade — every exponent is exactly halved.
(In ℤⁿ this is typable only at even exponent vectors: Kennedy's
``sqrt : real d² → real d.)
sqrt(Dim dim)(in (constant) uom_quantity_rational_exponents.Dim uom_quantity_rational_exponents.dim = Dim(Rational(0, 1), Rational(2, 1), Rational(0, 1))Quantity!(constant) uom_quantity_rational_exponents.Dim uom_quantity_rational_exponents.dim = Dim(Rational(0, 1), Rational(0, 1), Rational(2, 1))dim (parameter) const(uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(0, 1), Rational(2, 1)))) qq)
in ((parameter) const(uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(0, 1), Rational(2, 1)))) qq.(field) double uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(0, 1), Rational(2, 1))).valuevalue >= 0, "sqrt of a negative quantity")
{
import (package) stdstd.(module) std.mathContains the elementary mathematical functions (powers, roots,
and trigonometric functions), and low-level floating-point operations.
Mathematical special functions are available in std.mathspecial.
Category Members Constants E PI PI_2 PI4 M1_PI M2_PI M2_SQRTPI LN10 LN2 LOG2 LOG2E LOG2T LOG10E SQRT2 SQRT1_2 Algebraic abs fabs sqrt cbrt hypot poly nextPow2 truncPow2 Trigonometry sin cos tan asin acos atan atan2 sinh cosh tanh asinh acosh atanh Rounding ceil floor round lround trunc rint lrint nearbyint rndtol quantize Exponentiation & Logarithms pow powmod exp exp2 expm1 ldexp frexp log log2 log10 logb ilogb log1p scalbn Remainder fmod modf remainder remquo Floating-point operations approxEqual feqrel fdim fmax fmin fma isClose nextDown nextUp nextafter NaN getNaNPayload cmp Introspection isFinite isIdentical isInfinity isNaN isNormal isSubnormal signbit sgn copysign isPowerOf2 Hardware Control IeeeFlags ieeeFlags resetIeeeFlags FloatingPointControl
The functionality closely follows the IEEE754-2008 standard for
floating-point arithmetic, including the use of camelCase names rather
than C99-style lower case names. All of these functions behave correctly
when presented with an infinity or NaN.
The following IEEE 'real' formats are currently supported:
64 bit Big-endian 'double' (eg PowerPC)
128 bit Big-endian 'quadruple' (eg SPARC)
64 bit Little-endian 'double' (eg x86-SSE2)
80 bit Little-endian, with implied bit 'real80' (eg x87, Itanium)
128 bit Little-endian 'quadruple' (not implemented on any known processor!)
Non-IEEE 128 bit Big-endian 'doubledouble' (eg PowerPC) has partial support
Unlike C, there is no global 'errno' variable. Consequently, almost all of
these functions are pure nothrow.
Source
std/math/package.d
math : (alias) stdSqrt = float std.math.algebraic.sqrt(float x) pure nothrow @nogc @safeCompute square root of x.
$(TABLE_SV
$(TR $(TH x) $(TH sqrt(x)) $(TH invalid?))
$(TR $(TD -0.0) $(TD -0.0) $(TD no))
$(TR $(TD $(LT)0.0) $(TD $(NAN)) $(TD yes))
$(TR $(TD +$(INFIN)) $(TD +$(INFIN)) $(TD no))
)
stdSqrt = (alias) stdSqrt = float std.math.algebraic.sqrt(float x) pure nothrow @nogc @safeCompute square root of x.
$(TABLE_SV
$(TR $(TH x) $(TH sqrt(x)) $(TH invalid?))
$(TR $(TD -0.0) $(TD -0.0) $(TD no))
$(TR $(TD $(LT)0.0) $(TD $(NAN)) $(TD yes))
$(TR $(TD +$(INFIN)) $(TD +$(INFIN)) $(TD no))
)
sqrt;
return (template instance) uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(0, 1), Rational(1, 1)))Quantity!(uom_quantity_rational_exponents.Dim uom_quantity_rational_exponents.halved(in uom_quantity_rational_exponents.Dim d) pure nothrow @nogc @safeHalves every exponent — the dimension-level image of sqrt, total on
every grade because ℚ³ is divisible.
halved((constant) uom_quantity_rational_exponents.Dim uom_quantity_rational_exponents.dim = Dim(Rational(0, 1), Rational(2, 1), Rational(0, 1))dim))(double std.math.algebraic.sqrt(double x) pure nothrow @nogc @safeCompute square root of x.
x sqrt(x) invalid? -0.0 -0.0 no <0.0 yes + + no
stdSqrt((parameter) const(uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(0, 1), Rational(2, 1)))) qq.(field) double uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(0, 1), Rational(2, 1))).valuevalue));
}
void void D main() @safemain() @safe
{
import (package) stdstd.(module) std.mathContains the elementary mathematical functions (powers, roots,
and trigonometric functions), and low-level floating-point operations.
Mathematical special functions are available in std.mathspecial.
Category Members Constants E PI PI_2 PI4 M1_PI M2_PI M2_SQRTPI LN10 LN2 LOG2 LOG2E LOG2T LOG10E SQRT2 SQRT1_2 Algebraic abs fabs sqrt cbrt hypot poly nextPow2 truncPow2 Trigonometry sin cos tan asin acos atan atan2 sinh cosh tanh asinh acosh atanh Rounding ceil floor round lround trunc rint lrint nearbyint rndtol quantize Exponentiation & Logarithms pow powmod exp exp2 expm1 ldexp frexp log log2 log10 logb ilogb log1p scalbn Remainder fmod modf remainder remquo Floating-point operations approxEqual feqrel fdim fmax fmin fma isClose nextDown nextUp nextafter NaN getNaNPayload cmp Introspection isFinite isIdentical isInfinity isNaN isNormal isSubnormal signbit sgn copysign isPowerOf2 Hardware Control IeeeFlags ieeeFlags resetIeeeFlags FloatingPointControl
The functionality closely follows the IEEE754-2008 standard for
floating-point arithmetic, including the use of camelCase names rather
than C99-style lower case names. All of these functions behave correctly
when presented with an infinity or NaN.
The following IEEE 'real' formats are currently supported:
64 bit Big-endian 'double' (eg PowerPC)
128 bit Big-endian 'quadruple' (eg SPARC)
64 bit Little-endian 'double' (eg x86-SSE2)
80 bit Little-endian, with implied bit 'real80' (eg x87, Itanium)
128 bit Little-endian 'quadruple' (not implemented on any known processor!)
Non-IEEE 128 bit Big-endian 'doubledouble' (eg PowerPC) has partial support
Unlike C, there is no global 'errno' variable. Consequently, almost all of
these functions are pure nothrow.
Source
std/math/package.d
math : (alias constant) PI = real std.math.constants.PI = 3.14159Lπ = 3.141592...
PI;
import (package) stdstd.(module) std.stdioCategory Symbols File handles _popen File isFileHandle openNetwork stderr stdin stdout Reading chunks lines readf readfln readln Writing toFile write writef writefln writeln Misc KeepTerminator LockType StdioException
Standard I/O functions that extend core.stdc.stdio. core.stdc.stdio
is publically imported when importing std.stdio.
There are three layers of I/O:
The lowest layer is the operating system layer. The two main schemes are Windows and Posix.
C's stdio.h which unifies the two operating system schemes.
std.stdio, this module, unifies the various stdio.h implementations into
a high level package for D programs.
Source
std/stdio.d
stdio : (alias template) writeln = std.stdio.writeln(T...)(T args)Equivalent to write(args, '\n'). Calling writeln without
arguments is valid and just prints a newline to the standard
output.
Params:
args = the items to write to stdout
Throws:
In case of an I/O error, throws an $(LREF StdioException).
Example:
Reads stdin and writes it to stdout with an argument
counter.
import std.stdio;
void main()
{
string line;
for (size_t count = 0; (line = readln) !is null; count++)
{
writeln("Input ", count, ": ", line);
}
}
---
writeln;
auto (local variable) uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(2, 1), Rational(0, 1))) areaarea = (template instance) uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(2, 1), Rational(0, 1)))Quantity!((struct) uom_quantity_rational_exponents.DimA dimension: one element of ℚ³ over (mass, length, time), stored as
normalized rational exponents.
Dim(length: (struct) uom_quantity_rational_exponents.RationalA rational exponent kept in unique normal form: gcd(num, den) == 1 and
den > 0. Normalization is what makes type identity work — equal
exponents are bit-identical template arguments, so 2/2 and 1/1 name
the same dimension.
Rational(2)))(156.25); // 156.25 m^2
auto (local variable) uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(1, 1), Rational(0, 1))) sideside = uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(1, 1), Rational(0, 1))) uom_quantity_rational_exponents.sqrt!(Dim(Rational(0, 1), Rational(2, 1), Rational(0, 1)))(in uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(2, 1), Rational(0, 1))) q) pure nothrow @nogc @safesqrt over ℚ³: total on every grade — every exponent is exactly halved.
(In ℤⁿ this is typable only at even exponent vectors: Kennedy's
``sqrt : real d² → real d.)
sqrt((local variable) uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(2, 1), Rational(0, 1))) areaarea);
// Normalization pays off here: halving 2/1 yields exactly 1/1, so
// sqrt(area) has the *same type* as any other length ...
static assert(is(typeof((local variable) uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(1, 1), Rational(0, 1))) sideside) == Quantity!(Dim(length: Rational(1)))));
auto (local variable) uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(1, 1), Rational(0, 1))) metremetre = (template instance) uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(1, 1), Rational(0, 1)))Quantity!(Dim(length: Rational(1)))(1.0);
static assert(__traits(compiles, (local variable) uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(1, 1), Rational(0, 1))) sideside + (local variable) uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(1, 1), Rational(0, 1))) metremetre));
// ... and m^(1/2) is a first-class grade of its own ...
auto (local variable) uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(1, 2), Rational(0, 1))) rootSiderootSide = uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(1, 2), Rational(0, 1))) uom_quantity_rational_exponents.sqrt!(Dim(Rational(0, 1), Rational(1, 1), Rational(0, 1)))(in uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(1, 1), Rational(0, 1))) q) pure nothrow @nogc @safesqrt over ℚ³: total on every grade — every exponent is exactly halved.
(In ℤⁿ this is typable only at even exponent vectors: Kennedy's
``sqrt : real d² → real d.)
sqrt((local variable) uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(1, 1), Rational(0, 1))) sideside);
static assert(is(typeof((local variable) uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(1, 2), Rational(0, 1))) rootSiderootSide) == Quantity!(Dim(length: Rational(1, 2)))));
// ... but it is NOT a length: adding m^(1/2) to m is rejected at compile
// time. This assert holds precisely because the addition does not compile.
static assert(!__traits(compiles, (local variable) uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(1, 2), Rational(0, 1))) rootSiderootSide + (local variable) uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(1, 1), Rational(0, 1))) sideside),
"adding m^(1/2) to m must not compile");
// A fractional grade can be transient: the pendulum period
// T = 2π·sqrt(L/g) passes through sqrt over s² and lands back in the
// integer lattice.
auto (local variable) uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(1, 1), Rational(0, 1))) pendulumpendulum = (template instance) uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(1, 1), Rational(0, 1)))Quantity!(Dim(length: Rational(1)))(2.5); // 2.5 m
auto (local variable) uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(1, 1), Rational(-2, 1))) gravitygravity = // toy g = 10 m/s²
(template instance) uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(1, 1), Rational(-2, 1)))Quantity!((struct) uom_quantity_rational_exponents.DimA dimension: one element of ℚ³ over (mass, length, time), stored as
normalized rational exponents.
Dim(length: (struct) uom_quantity_rational_exponents.RationalA rational exponent kept in unique normal form: gcd(num, den) == 1 and
den > 0. Normalization is what makes type identity work — equal
exponents are bit-identical template arguments, so 2/2 and 1/1 name
the same dimension.
Rational(1), time: (struct) uom_quantity_rational_exponents.RationalA rational exponent kept in unique normal form: gcd(num, den) == 1 and
den > 0. Normalization is what makes type identity work — equal
exponents are bit-identical template arguments, so 2/2 and 1/1 name
the same dimension.
Rational(-2)))(10.0);
auto (local variable) uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(0, 1), Rational(1, 1))) periodperiod = 2.0 * (constant) real std.math.constants.PI = 3.14159Lπ = 3.141592...
PI * uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(0, 1), Rational(1, 1))) uom_quantity_rational_exponents.sqrt!(Dim(Rational(0, 1), Rational(0, 1), Rational(2, 1)))(in uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(0, 1), Rational(2, 1))) q) pure nothrow @nogc @safesqrt over ℚ³: total on every grade — every exponent is exactly halved.
(In ℤⁿ this is typable only at even exponent vectors: Kennedy's
``sqrt : real d² → real d.)
sqrt((local variable) uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(1, 1), Rational(0, 1))) pendulumpendulum / uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(0, 1), Rational(2, 1))) uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(1, 1), Rational(0, 1))).opBinary!("/", Dim(Rational(0, 1), Rational(1, 1), Rational(-2, 1)))(in uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(1, 1), Rational(-2, 1))) rhs) const pure nothrow @nogc @safe*// are total: the result grade adds/subtracts exponent vectors.
gravity);
static assert(is(typeof((local variable) uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(0, 1), Rational(1, 1))) periodperiod) == Quantity!(Dim(time: Rational(1)))));
void std.stdio.writeln!(string, uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(2, 1), Rational(0, 1))))(string __param_0, uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(2, 1), Rational(0, 1))) __param_1) @safeEquivalent to write(args, '\n'). Calling writeln without
arguments is valid and just prints a newline to the standard
output.
Example
Reads stdin and writes it to stdout with an argument
counter.
import std.stdio;
void main()
{
string line;
for (size_t count = 0; (line = readln) !is null; count++)
{
writeln("Input ", count, ": ", line);
}
}
writeln("area = ", (local variable) uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(2, 1), Rational(0, 1))) areaarea);
void std.stdio.writeln!(string, uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(1, 1), Rational(0, 1))), string)(string __param_0, uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(1, 1), Rational(0, 1))) __param_1, string __param_2) @safeEquivalent to write(args, '\n'). Calling writeln without
arguments is valid and just prints a newline to the standard
output.
Example
Reads stdin and writes it to stdout with an argument
counter.
import std.stdio;
void main()
{
string line;
for (size_t count = 0; (line = readln) !is null; count++)
{
writeln("Input ", count, ": ", line);
}
}
writeln("sqrt(area) = ", (local variable) uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(1, 1), Rational(0, 1))) sideside, " (a plain length: 2/2 normalizes to 1)");
void std.stdio.writeln!(string, uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(1, 2), Rational(0, 1))), string)(string __param_0, uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(1, 2), Rational(0, 1))) __param_1, string __param_2) @safeEquivalent to write(args, '\n'). Calling writeln without
arguments is valid and just prints a newline to the standard
output.
Example
Reads stdin and writes it to stdout with an argument
counter.
import std.stdio;
void main()
{
string line;
for (size_t count = 0; (line = readln) !is null; count++)
{
writeln("Input ", count, ": ", line);
}
}
writeln("sqrt(side) = ", (local variable) uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(1, 2), Rational(0, 1))) rootSiderootSide, " (a first-class fractional grade)");
void std.stdio.writeln!(string, uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(0, 1), Rational(1, 1))), string)(string __param_0, uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(0, 1), Rational(1, 1))) __param_1, string __param_2) @safeEquivalent to write(args, '\n'). Calling writeln without
arguments is valid and just prints a newline to the standard
output.
Example
Reads stdin and writes it to stdout with an argument
counter.
import std.stdio;
void main()
{
string line;
for (size_t count = 0; (line = readln) !is null; count++)
{
writeln("Input ", count, ": ", line);
}
}
writeln("period = ", (local variable) uom_quantity_rational_exponents.Quantity!(Dim(Rational(0, 1), Rational(0, 1), Rational(1, 1))) periodperiod, " (2π·sqrt(L/g) — back in the integer lattice)");
}