cc [ flag ... ] file ... -lm [ library ... ] #include <math.h>double expm1(double x);
If x is NaN, then the function returns NaN.
If x is positive infinity, expm1() returns positive infinity.
If x is negative infinity, expm1() returns -1.0.
If the value overflows, expm1() returns HUGE_VAL.
No errors will occur.
The value of expm1(x) may be more accurate than exp(x)-1.0 for small values of x.
The expm1() and log1p(3M) functions are useful for financial calculations of ((1+x)n-1)/x, namely:
expm1(n * log1p(x)) / x
when x is very small (for example, when performing calculations with a small daily interest rate). These functions also simplify writing accurate inverse hyperbolic functions.
See attributes(5) for descriptions of the following attributes:
|ATTRIBUTE TYPE||ATTRIBUTE VALUE|