PHPerKaigi 2024

expm1

(PHP 4 >= 4.1.0, PHP 5, PHP 7, PHP 8)

expm1 Returns exp($num) - 1, computed in a way that is accurate even when the value of number is close to zero

Description

expm1(float $num): float

expm1() returns the equivalent to exp($num) - 1 computed in a way that is accurate even if the value of num is near zero, a case where exp($num) - 1 would be inaccurate due to subtraction of two numbers that are nearly equal.

Parameters

num

The argument to process

Return Values

e to the power of num, minus one.

See Also

  • log1p() - Returns log(1 + number), computed in a way that is accurate even when the value of number is close to zero
  • exp() - Calculates the exponent of e

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