NAME

log - natural logarithm function

 SYNOPSIS

#include <math.h>

double log(double x);

 DESCRIPTION

The log() function computes the natural logarithm of x, log_e(x). The value of x must be positive.

An application wishing to check for error situations should set errno to 0 before calling log(). If errno is non-zero on return, or the return value is NaN, an error has occurred.

 RETURN VALUE

Upon successful completion, log() returns the natural logarithm of x.

If x is NaN, NaN is returned and errno may be set to [EDOM].

If x is less than 0,  -HUGE_VAL or NaN is returned,  and errno is set to [EDOM].

If x is 0, -HUGE_VAL is returned and errno may be set to [ERANGE].

 ERRORS

The log() function will fail if:

[EDOM]

The value of x is negative.

The log() function may fail if:

[EDOM]

The value of x is NaN.

[ERANGE]

The value of x is 0.

No other errors will occur.

 EXAMPLES

None.

 APPLICATION USAGE

None.

 FUTURE DIRECTIONS

None.

 SEE ALSO

exp(), isnan(), log10(), log1p(), <math.h>.

DERIVATION

Derived from Issue 1 of the SVID.