# logbl(3m) [sunos man page]

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

logb, logbf, logbl - radix-independent exponentSYNOPSIS

cc [ flag... ] file...[ library... ] #include <math.h> double logb(double x); float logbf(float x); long double logbl(long double x);-lmDESCRIPTION

These functions compute the exponent of x, which is the integral part of logr |x|, as a signed floating point value, for non-zero x, where r is the radix of the machine's floating-point arithmetic, which is the value of FLT_RADIX defined in the <float.h> header.RETURN VALUES

Upon successful completion, these functions return the exponent of x. If x is subnormal: o For SUSv3-conforming applications (see standards(5)), the exponent of x as if x were normalized is returned. o Otherwise,,-1022, and-126are returned for logb(), logbf(), and logbl(), respectively. If x is +-0, a pole error occurs and logb(), logbf(), and logbl() return-16382,-HUGE_VAL, and-HUGE_VALF, respectively. If x is NaN, a NaN is returned. If x is +-Inf, +Inf is returned.-HUGE_VALLERRORS

These functions will fail if: 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. The logb() function sets errno to EDOM if the value of x is 0.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 logb(). On return, if errno is non-zero, an error has occurred. The logbf() and logbl() 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), ilogb(3M), math.h(3HEAD), matherr(3M), scalb(3M), attributes(5), standards(5)SunOS 5.101 Nov 2003 logb(3M)

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

logb, logbf, logbl - radix-independent exponentSYNOPSIS

c99 [ flag... ] file...[ library... ] #include <math.h> double logb(double x); float logbf(float x); long double logbl(long double x); cc [ flag... ] file...-lm[ library... ] #include <math.h> double logb(double x); float logbf(float x); long double logbl(long double x);-lmDESCRIPTION

These functions compute the exponent of x, which is the integral part of log(r) |x|, as a signed floating point value, for non-zero x, where r is the radix of the machine's floating-point arithmetic, which is the value of FLT_RADIX defined in the <float.h> header.RETURN VALUES

Upon successful completion, these functions return the exponent of x. If x is subnormal: o For SUSv3-conforming applications compiled with the c99 compiler driver (see standards(5)), the exponent of x as if x were nor- malized is returned. o Otherwise, if compiled with the cc compiler driver,,-1022, and-126are returned for logb(), logbf(), and logbl(), respectively. If x is +-0, a pole error occurs and logb(), logbf(), and logbl() return-16382,-HUGE_VAL, and-HUGE_VALF, respectively. If x is NaN, a NaN is returned. If x is +-Inf, +Inf is returned.-HUGE_VALLERRORS

These functions will fail if: 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. The logb() function sets errno to EDOM if the value of x is 0.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 logb(). On return, if errno is non-zero, an error has occurred. The logbf() and logbl() 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), ilogb(3M), math.h(3HEAD), matherr(3M), scalb(3M), attributes(5), standards(5)SunOS 5.1112 Jul 2006 logb(3M)