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std.math.pow - multiple declarations

Function pow

Compute the value of x n, where n is an integer

Unqual!F pow(F, G) (
  F x,
  G n
) pure nothrow @nogc @trusted
if (isFloatingPoint!F && isIntegral!G);

Example

writeln(pow(2.0, 5)); // 32.0
assert(pow(1.5, 9).feqrel(38.4433) > 16);
assert(pow(real.nan, 2) is real.nan);
writeln(pow(real.infinity, 2)); // real.infinity

Function pow

Compute the power of two integral numbers.

typeof(Unqual!F.init*Unqual!G.init) pow(F, G) (
  F x,
  G n
) pure nothrow @nogc @trusted
if (isIntegral!F && isIntegral!G);

Parameters

NameDescription
x base
n exponent

Returns

x raised to the power of n. If n is negative the result is 1 / pow(x, -n), which is calculated as integer division with remainder. This may result in a division by zero error.

If both x and n are 0, the result is 1.

Throws

If x is 0 and n is negative, the result is the same as the result of a division by zero.

Example

writeln(pow(2, 3)); // 8
writeln(pow(3, 2)); // 9

writeln(pow(2, 10)); // 1_024
writeln(pow(2, 20)); // 1_048_576
writeln(pow(2, 30)); // 1_073_741_824

writeln(pow(0, 0)); // 1

writeln(pow(1, -5)); // 1
writeln(pow(1, -6)); // 1
writeln(pow(-1, -5)); // -1
writeln(pow(-1, -6)); // 1

writeln(pow(-2, 5)); // -32
writeln(pow(-2, -5)); // 0
writeln(pow(cast(double)-2, -5)); // -0.03125

Function pow

Computes integer to floating point powers.

real pow(I, F) (
  I x,
  F y
) pure nothrow @nogc @trusted
if (isIntegral!I && isFloatingPoint!F);

Example

writeln(pow(2, 5.0)); // 32.0
writeln(pow(7, 3.0)); // 343.0
assert(pow(2, real.nan) is real.nan);
writeln(pow(2, real.infinity)); // real.infinity

Function pow

Calculates xy.

Unqual!(Largest!(F,G)) pow(F, G) (
  F x,
  G y
) pure nothrow @nogc @trusted
if (isFloatingPoint!F && isFloatingPoint!G);

Special Values
x y pow(x, y) div 0 invalid?
anything ±0.0 1.0 no no
|x| > 1 +∞ +∞ no no
|x| < 1 +∞ +0.0 no no
|x| > 1 -∞ +0.0 no no
|x| < 1 -∞ +∞ no no
+∞ > 0.0 +∞ no no
+∞ < 0.0 +0.0 no no
-∞ odd integer > 0.0 -∞ no no
-∞ > 0.0, not odd integer +∞ no no
-∞ odd integer < 0.0 -0.0 no no
-∞ < 0.0, not odd integer +0.0 no no
±1.0 ±∞ -NAN no yes
< 0.0 finite, nonintegral NAN no yes
±0.0 odd integer < 0.0 ±∞ yes no
±0.0 < 0.0, not odd integer +∞ yes no
±0.0 odd integer > 0.0 ±0.0 no no
±0.0 > 0.0, not odd integer +0.0 no no

Example

assert(isClose(pow(2.0, 3.0), 8.0));
assert(isClose(pow(1.5, 10.0), 57.6650390625));

// square root of 9
assert(isClose(pow(9.0, 0.5), 3.0));
// 10th root of 1024
assert(isClose(pow(1024.0, 0.1), 2.0));

assert(isClose(pow(-4.0, 3.0), -64.0));

// reciprocal of 4 ^^ 2
assert(isClose(pow(4.0, -2.0), 0.0625));
// reciprocal of (-2) ^^ 3
assert(isClose(pow(-2.0, -3.0), -0.125));

assert(isClose(pow(-2.5, 3.0), -15.625));
// reciprocal of 2.5 ^^ 3
assert(isClose(pow(2.5, -3.0), 0.064));
// reciprocal of (-2.5) ^^ 3
assert(isClose(pow(-2.5, -3.0), -0.064));

// reciprocal of square root of 4
assert(isClose(pow(4.0, -0.5), 0.5));

// per definition
assert(isClose(pow(0.0, 0.0), 1.0));

Example

// the result is a complex number
// which cannot be represented as floating point number
import std.math : isNaN;
assert(isNaN(pow(-2.5, -1.5)));

// use the ^^-operator of std.complex instead
import std.complex : complex;
auto c1 = complex(-2.5, 0.0);
auto c2 = complex(-1.5, 0.0);
auto result = c1 ^^ c2;
// exact result apparently depends on `real` precision => increased tolerance
assert(isClose(result.re, -4.64705438e-17, 2e-4));
assert(isClose(result.im, 2.52982e-1, 2e-4));

Authors

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

License

Boost License 1.0.