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HP-UX 11i Version 1.5 Reference Volume 4, Section 3: Libraries > l
log(3M) |
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NAMElog(), logf(), logl(), logw(), logq() — natural logarithm functions DESCRIPTIONlog() returns the natural logarithm of x. logf() is a float version of log(); it takes a float argument and returns a float result. USAGETo use these functions, compile either with the default -Ae option or with the -Aa and the -D_HPUX_SOURCE options. To use (for IA-64 systems) logw() or logq(), compile also with the -fpwidetypes option. To use any of these functions, make sure your program includes <math.h>, and link in the math library by specifying -lm on the compiler or linker command line. For more information, see the HP-UX Floating-Point Guide. PA-RISC ONLY:Millicode versions of the log() and logf() functions are available. Millicode versions of math library functions are usually faster than their counterparts in the standard library. To use these versions, compile your program with the +Olibcalls or the +Oaggressive optimization option. For special cases, the millicode versions return the value described in the RETURN VALUE section, but do not set errno. RETURN VALUEIf x is +INFINITY, log() returns +INFINITY. If x is zero, log() returns -HUGE_VAL (equal to -INFINITY) and raises the divide-by-zero exception. If x is less than zero, log() returns NaN and raises the invalid exception. If x is NaN, log() returns NaN. When it raises no other exception, whether log() raises the inexact exception is unspecified. |
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