man3/log2.3

   1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
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  23 .\" References consulted:
  24 .\"     Linux libc source code
  25 .\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
  26 .\"     386BSD man pages
  27 .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
  28 .\" Modified 1995-08-14 by Arnt Gulbrandsen <agulbra@troll.no>
  29 .\" Modified 2002-07-27 by Walter Harms
  30 .\"     (walter.harms@informatik.uni-oldenburg.de)
  31 .\"
  32 .TH LOG2 3  2002-07-27  "" "Linux Programmer's Manual"
  33 .SH NAME
  34 log2, log2f, log2l \- base-2 logarithmic function
  35 .SH SYNOPSIS
  36 .nf
  37 .B #include <math.h>
  38 .sp
  39 .BI "double log2(double " x );
  40 .br
  41 .BI "float log2f(float " x );
  42 .br
  43 .BI "long double log2l(long double " x );
  44 .fi
  45 .sp
  46 Compile with \-std=c99; link with \-lm.
  47 .SH DESCRIPTION
  48 The \fBlog2\fP() function returns the base 2 logarithm of \fIx\fP.
  49 .SH ERRORS
  50 The \fBlog2\fP() function can return the following error:
  51 .TP
  52 .B EDOM
  53 The argument \fIx\fP is negative.
  54 .TP
  55 .B ERANGE
  56 The argument \fIx\fP is zero.
  57 The log of zero is not defined
  58 (minus infinity).
  59 .SH "CONFORMING TO"
  60 SVr4, 4.3BSD, C89.
  61 The
  62 .I float
  63 and
  64 .I "long double"
  65 variants are C99 requirements.
  66 .SH "SEE ALSO"
  67 .BR cbrt (3),
  68 .BR clog2 (3),
  69 .BR sqrt (3)