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LOG(3) NetBSD Library Functions Manual LOG(3)
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Maintained for NetBSD
by Kimmo Suominen.
Based on man-cgi by Panagiotis Christias.
log, logf, log10, log10f, log1p, log1pf log2, log2f, -- logarithm func-
Math Library (libm, -lm)
The following functions compute logarithms:
· The log() and logf() functions return the natural logarithm.
· The log10() and log10f() functions return the base 10 logarithm.
· The log1p() and log1pf() functions return the natural logarithm of
(1.0 + x) accurately even for very small values of x.
· The log2() and log2f() functions return the base 2 logarithm.
Upon successful completion, the functions return the logarithm of x as
descibed above. Otherwise the following may occur:
1. If x is NaN, all functions return NaN.
2. If x is positive infinity, all functions return x. If x is
negative infinity, all functions return NaN.
3. If x is +0.0 or -0.0, the log(), log10(), and log2() families
return either -HUGE_VAL, -HUGE_VALF, or -HUGE_VALL, whereas
the log1p() family returns x.
4. If x is +1.0, the log(), log10(), and log2() families return
+0.0. If x is -1.0, the log1p() family returns -HUGE_VAL,
-HUGE_VALF, or -HUGE_VALL.
In addition, on a VAX, errno is set to EDOM and the reserved operand is
returned by log() unless x > 0, by log1p() unless x > -1.
exp(3), ilogb(3), math(3)
The described functions conform to ISO/IEC 9899:1999 (``ISO C99'').
The history of the logarithm functions dates back to Version 6 AT&T UNIX.
NetBSD 6.0 September 13, 2011 NetBSD 6.0