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Function std.math.exponential.log1p
Calculates the natural logarithm of 1 + x.
real log1p
(
real x
) pure nothrow @nogc @safe;
For very small x, log1p(x) will be more accurate than log(1 + x).
x | log1p(x) | divide by 0? | invalid? |
---|---|---|---|
±0.0 | ±0.0 | no | no |
-1.0 | -∞ | yes | no |
<-1.0 | -NAN | no | yes |
+∞ | +∞ | no | no |
Example
import std .math .traits : isIdentical, isNaN;
import std .math .operations : feqrel;
assert(isIdentical(log1p(0.0), 0.0));
assert(log1p(1.0) .feqrel(0.69314) > 16);
writeln(log1p(-1.0)); // -real.infinity
assert(isNaN(log1p(-2.0)));
assert(log1p(real .nan) is real .nan);
assert(log1p(-real .nan) is -real .nan);
writeln(log1p(real .infinity)); // real.infinity
Authors
Walter Bright, Don Clugston, Conversion of CEPHES math library to D by Iain Buclaw and David Nadlinger
License
Copyright © 1999-2022 by the D Language Foundation | Page generated by ddox.