Mathematical Library Functions                            log(3M)


log - natural logarithm function


cc [ flag ... ] file ... -lm [ library ... ] #include <math.h> double log(double x);


The log() function computes the natural logarithm of x, loge(x). The value of x must be positive. RETURN VALUES Upon successful completion, log() returns the natural loga- rithm of x. If x is NaN, NaN is returned. 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. In IEEE754 mode (the -Xlibmieee cc compilation option), if x is Inf or a quiet NaN, x is returned; if x is a signaling NaN, a quiet NaN is returned and the invalid operation exception is raised; if x is 1, 0 is returned; for all other positive x, a normalized number is returned and the inexact exception is raised. For exceptional cases, matherr(3M) tabulates the values to be returned as dictated by Standards other than XPG4. ERRORS The log() function will fail if: EDOM The value of x is negative. The log() function may fail if: ERANGE The value of x is 0. No other errors will occur. USAGE 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. SunOS 5.8 Last change: 29 Dec 1996 1 Mathematical Library Functions log(3M)


See attributes(5) for descriptions of the following attri- butes: ____________________________________________________________ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | |_____________________________|_____________________________| | MT-Level | MT-Safe | |_____________________________|_____________________________|


exp(3M), isnan(3M), log10(3M), log1p(3M), matherr(3M), attributes(5), standards(5) SunOS 5.8 Last change: 29 Dec 1996 2