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  12 .TH ilogb 3M "12 Jul 2006" "SunOS 5.11" "Mathematical Library Functions"
  13 .SH NAME
  14 ilogb, ilogbf, ilogbl \- return an unbiased exponent
  15 .SH SYNOPSIS
  16 .LP
  17 .nf
  18 c99 [ \fIflag\fR... ] \fIfile\fR... \fB-lm\fR [ \fIlibrary\fR... ]
  19 #include <math.h>
  20 
  21 \fBint\fR \fBilogb\fR(\fBdouble\fR \fIx\fR);
  22 .fi
  23 
  24 .LP
  25 .nf
  26 \fBint\fR \fBilogbf\fR(\fBfloat\fR \fIx\fR);
  27 .fi
  28 
  29 .LP
  30 .nf
  31 \fBint\fR \fBilogbl\fR(\fBlong double\fR \fIx\fR);
  32 .fi
  33 
  34 .LP
  35 .nf
  36 cc [ \fIflag\fR... ] \fIfile\fR... \fB-lm\fR [ \fIlibrary\fR... ]
  37 #include <math.h>
  38 
  39 \fBint\fR \fBilogb\fR(\fBdouble\fR \fIx\fR);
  40 .fi
  41 
  42 .LP
  43 .nf
  44 \fBint\fR \fBilogbf\fR(\fBfloat\fR \fIx\fR);
  45 .fi
  46 
  47 .LP
  48 .nf
  49 \fBint\fR \fBilogbl\fR(\fBlong double\fR \fIx\fR);
  50 .fi
  51 
  52 .SH DESCRIPTION
  53 .sp
  54 .LP
  55 These functions return the exponent part of their argument \fIx\fR.  Formally,
  56 the return value is the integral part of  \fBlog\fR(r)| \fIx\fR | as a signed
  57 integral value, for non-zero \fIx\fR, where \fIr\fR is the radix of the
  58 machine's floating point arithmetic, which is the value of \fBFLT_RADIX\fR
  59 defined in <\fBfloat.h\fR>.
  60 .SH RETURN VALUES
  61 .sp
  62 .LP
  63 Upon successful completion, these functions return the exponent part of \fIx\fR
  64 as a signed integer value. They are equivalent to calling the corresponding
  65 \fBlogb\fR(3M) function and casting the returned value to type \fBint\fR.
  66 .sp
  67 .LP
  68 If \fIx\fR is 0, the value \fBFP_ILOGB0\fR is returned. For SUSv3-conforming
  69 applications compiled with the \fBc99\fR compiler driver (see
  70 \fBstandards\fR(5)), a domain error occurs.
  71 .sp
  72 .LP
  73 If \fIx\fR is \(+-Inf, the value \fBINT_MAX\fR is returned. For
  74 SUSv3-conforming applications compiled with the \fBc99\fR compiler driver, a
  75 domain error occurs.
  76 .sp
  77 .LP
  78 If \fIx\fR is NaN, the value \fBFP_ILOGBNAN\fR is returned. For
  79 SUSv3-conforming applications compiled with the \fBc99\fR compiler driver, a
  80 domain error occurs.
  81 .SH ERRORS
  82 .sp
  83 .LP
  84 These functions will fail if:
  85 .sp
  86 .ne 2
  87 .mk
  88 .na
  89 \fBDomain Error\fR
  90 .ad
  91 .RS 16n
  92 .rt  
  93 The \fIx\fR argument is zero, NaN, or \(+-Inf.
  94 .sp
  95 If the integer expression (\fBmath_errhandling\fR & \fBMATH_ERREXCEPT\fR) is
  96 non-zero, then the invalid floating-point exception is raised.
  97 .RE
  98 
  99 .SH ATTRIBUTES
 100 .sp
 101 .LP
 102 See \fBattributes\fR(5) for descriptions of the following attributes:
 103 .sp
 104 
 105 .sp
 106 .TS
 107 tab() box;
 108 cw(2.75i) |cw(2.75i) 
 109 lw(2.75i) |lw(2.75i) 
 110 .
 111 ATTRIBUTE TYPEATTRIBUTE VALUE
 112 _
 113 Interface StabilityStandard
 114 _
 115 MT-LevelMT-Safe
 116 .TE
 117 
 118 .SH SEE ALSO
 119 .sp
 120 .LP
 121 \fBfeclearexcept\fR(3M), \fBfetestexcept\fR(3M), \fBlimits.h\fR(3HEAD),
 122 \fBlogb\fR(3M), \fBmath.h\fR(3HEAD), \fBscalb\fR(3M), \fBattributes\fR(5),
 123 \fBstandards\fR(5)