std.math.traits - D Programming Language (original) (raw)

It contains several functions for introspection on numerical values.

Walter Bright, Don Clugston, Conversion of CEPHES math library to D by Iain Buclaw and David Nadlinger

pure nothrow @nogc @trusted bool isNaN(X)(X x)
if (isFloatingPoint!X);

Determines if x is NaN.

Parameters:

X x	a floating point number.

Returns:

true if x is Nan.

Examples:

assert( isNaN(float.init)); assert( isNaN(-double.init)); assert( isNaN(real.nan)); assert( isNaN(-real.nan)); assert(!isNaN(cast(float) 53.6)); assert(!isNaN(cast(real)-53.6));

pure nothrow @nogc @trusted bool isFinite(X)(X x);

Determines if x is finite.

Parameters:

X x	a floating point number.

Returns:

true if x is finite.

Examples:

assert( isFinite(1.23f)); assert( isFinite(float.max)); assert( isFinite(float.min_normal)); assert(!isFinite(float.nan)); assert(!isFinite(float.infinity));

pure nothrow @nogc @trusted bool isNormal(X)(X x);

Determines if x is normalized.

A normalized number must not be zero, subnormal, infinite nor NAN.

Parameters:

X x	a floating point number.

Returns:

true if x is normalized.

Examples:

float f = 3; double d = 500; real e = 10e+48;

assert(isNormal(f)); assert(isNormal(d)); assert(isNormal(e)); f = d = e = 0; assert(!isNormal(f)); assert(!isNormal(d)); assert(!isNormal(e)); assert(!isNormal(real.infinity)); assert(isNormal(-real.max)); assert(!isNormal(real.min_normal/4));

pure nothrow @nogc @trusted bool isSubnormal(X)(X x);

Determines if x is subnormal.

Subnormals (also known as "denormal number"), have a 0 exponent and a 0 most significant mantissa bit.

Parameters:

X x	a floating point number.

Returns:

true if x is a denormal number.

Examples:

import std.meta : AliasSeq;

static foreach (T; AliasSeq!(float, double, real)) {{ T f; for (f = 1.0; !isSubnormal(f); f /= 2) assert(f != 0); }}

pure nothrow @nogc @trusted bool isInfinity(X)(X x)
if (isFloatingPoint!X);

Determines if x is ±∞.

Parameters:

X x	a floating point number.

Examples:

assert(!isInfinity(float.init)); assert(!isInfinity(-float.init)); assert(!isInfinity(float.nan)); assert(!isInfinity(-float.nan)); assert(isInfinity(float.infinity)); assert(isInfinity(-float.infinity)); assert(isInfinity(-1.0f / 0.0f));

pure nothrow @nogc @trusted bool isIdentical(real x, real y);

Is the binary representation of x identical to y?

Examples:

enum test1 = isIdentical(1.0,1.0); enum test2 = isIdentical(real.nan,real.nan); enum test3 = isIdentical(real.infinity, real.infinity); enum test4 = isIdentical(real.infinity, real.infinity); enum test5 = isIdentical(0.0, 0.0);

assert(test1); assert(test2); assert(test3); assert(test4); assert(test5);

enum test6 = !isIdentical(0.0, -0.0); enum test7 = !isIdentical(real.nan, -real.nan); enum test8 = !isIdentical(real.infinity, -real.infinity);

assert(test6); assert(test7); assert(test8);

pure nothrow @nogc @trusted int signbit(X)(X x);

Return 1 if sign bit of e is set, 0 if not.

Examples:

assert(!signbit(float.nan)); assert(signbit(-float.nan)); assert(!signbit(168.1234f)); assert(signbit(-168.1234f)); assert(!signbit(0.0f)); assert(signbit(-0.0f)); assert(signbit(-float.max)); assert(!signbit(float.max));

assert(!signbit(double.nan)); assert(signbit(-double.nan)); assert(!signbit(168.1234)); assert(signbit(-168.1234)); assert(!signbit(0.0)); assert(signbit(-0.0)); assert(signbit(-double.max)); assert(!signbit(double.max));

assert(!signbit(real.nan)); assert(signbit(-real.nan)); assert(!signbit(168.1234L)); assert(signbit(-168.1234L)); assert(!signbit(0.0L)); assert(signbit(-0.0L)); assert(signbit(-real.max)); assert(!signbit(real.max));

pure nothrow @nogc @trusted R copysign(R, X)(R to, X from)
if (isFloatingPoint!R && isFloatingPoint!X);

pure nothrow @nogc @trusted R copysign(R, X)(X to, R from)
if (isIntegral!X && isFloatingPoint!R);

Parameters:

R to	the numeric value to use
X from	the sign value to use

Returns:

a value composed of to with from's sign bit.

Examples:

writeln(copysign(1.0, 1.0)); writeln(copysign(1.0, -0.0)); writeln(copysign(1UL, -1.0)); writeln(copysign(-1.0, -1.0)); writeln(copysign(real.infinity, -1.0)); assert(copysign(real.nan, 1.0) is real.nan); assert(copysign(-real.nan, 1.0) is real.nan); assert(copysign(real.nan, -1.0) is -real.nan);

pure nothrow @nogc @safe F sgn(F)(F x)
if (isFloatingPoint!F || isIntegral!F);

Returns -1 if x < 0, x if x == 0, 1 ifx > 0, and NAN if x==NAN.

Examples:

writeln(sgn(168.1234)); writeln(sgn(-168.1234)); writeln(sgn(0.0)); writeln(sgn(-0.0));

pure nothrow @nogc @safe bool isPowerOf2(X)(const X x)
if (isNumeric!X);

Check whether a number is an integer power of two.

Note that only positive numbers can be integer powers of two. This function always return false if x is negative or zero.

Returns:

true if x is an integer power of two.

Examples:

import std.math.exponential : pow;

assert( isPowerOf2(1.0L)); assert( isPowerOf2(2.0L)); assert( isPowerOf2(0.5L)); assert( isPowerOf2(pow(2.0L, 96))); assert( isPowerOf2(pow(2.0L, -77)));

assert(!isPowerOf2(-2.0L)); assert(!isPowerOf2(-0.5L)); assert(!isPowerOf2(0.0L)); assert(!isPowerOf2(4.315)); assert(!isPowerOf2(1.0L / 3.0L));

assert(!isPowerOf2(real.nan)); assert(!isPowerOf2(real.infinity));

Examples:

assert( isPowerOf2(1)); assert( isPowerOf2(2)); assert( isPowerOf2(1uL << 63));

assert(!isPowerOf2(-4)); assert(!isPowerOf2(0)); assert(!isPowerOf2(1337u));