# log2f(3m) [opensolaris man page]

log2(3M) Mathematical Library Functions log2(3M)NAME

log2, log2f, log2l - compute base 2 logarithm functionsSYNOPSIS

c99 [ flag... ] file...[ library... ] #include <math.h> double log2(double x); float log2f(float x); long double log2l(long double x);-lmDESCRIPTION

These functions compute the base 2 logarithm of their argument x, log2(x).RETURN VALUES

Upon successful completion, these functions return the base 2 logarithm of x. If x is +-0, a pole error occurs and log2(), log2f(), and log2l() return,-HUGE_VAL, and-HUGE_VALF, respectively. For finite values of x that are less than 0, or if x is-HUGE_VALLa domain error occurs and a NaN is returned. If x is NaN, a NaN is returned. If x is 1, +0 is returned. If x is +Inf, x is returned.-InfERRORS

These functions will fail if: Domain Error The finite value of x is less than 0, or x isIf the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the invalid floating-point exception is raised. Pole Error The value of x is 0. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the divide-by-zero floating-point exception is raised.-Inf.USAGE

An application wanting to check for exceptions should call feclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, if fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an exception has been raised. An application should either examine the return value or check the floating point exception flags to detect exceptions.ATTRIBUTES

See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ |MT-Level |MT-Safe | +-----------------------------+-----------------------------+SEE ALSO

feclearexcept(3M), fetestexcept(3M), log(3M), math.h(3HEAD), attributes(5), standards(5)SunOS 5.1112 Jul 2006 log2(3M)

## Check Out this Related Man Page

log10(3M) Mathematical Library Functions log10(3M)NAME

log10, log10f, log10l - base 10 logarithm functionSYNOPSIS

c99 [ flag... ] file...[ library... ] #include <math.h> double log10(double x); float log10f(float x); long double log10l(long double x);-lmDESCRIPTION

These functions compute the base 10 logarithm of x, log(10)(x).RETURN VALUES

Upon successful completion, log10() returns the base 10 logarithm of x. If x is +-0, a pole error occurs and log10(), log10f(), and log10l() return,-HUGE_VAL, and-HUGE_VALF, respectively. For finite values of x that are less than 0, or if x is-HUGE_VALL, a domain error occurs and a NaN is returned. If x is NaN, a NaN is returned. If x is 1, +0 is returned. If x is +Inf, x is returned. For exceptional cases, matherr(3M) tabulates the values to be returned by log10() as specified by SVID3 and XPG3.-InfERRORS

These functions will fail if: Domain Error The finite value of x is negative, or x isIf the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, the invalid floating-point exception is raised. The log10() function sets errno to EDOM if the value of x is negative. Pole Error The value of x is 0. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, the divide-by-zero floating-point exception is raised.-Inf.USAGE

An application wanting to check for exceptions should call feclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, if fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an exception has been raised. An application should either examine the return value or check the floating point exception flags to detect exceptions. An application can also set errno to 0 before calling log10(). On return, if errno is non-zero, an error has occurred. The log10f() and log10l() functions do not set errno.ATTRIBUTES

See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ |MT-Level |MT-Safe | +-----------------------------+-----------------------------+SEE ALSO

feclearexcept(3M), fetestexcept(3M), isnan(3M), log(3M), math.h(3HEAD), matherr(3M), pow(3M), attributes(5), standards(5)SunOS 5.1112 Jul 2006 log10(3M)