xref: /freebsd/lib/libc/gen/fpclassify.3 (revision 5d62092f9440cea08dd1af170f272671d36499b9)

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.Dd February 12, 2003
.Dt FPCLASSIFY 3
.Os
.Sh NAME
.Nm fpclassify , isfinite , isinf , isnan , isnormal
.Nd "classify a floating-point number"
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In math.h
.Ft int
.Fn fpclassify "real-floating x"
.Ft int
.Fn isfinite "real-floating x"
.Ft int
.Fn isinf "real-floating x"
.Ft int
.Fn isnan "real-floating x"
.Ft int
.Fn isnormal "real-floating x"
.Sh DESCRIPTION
The
.Fn fpclassify
macro takes an argument of
.Va x
and returns one of the following manifest constants.
.Bl -tag -width ".Dv FP_SUBNORMAL"
.It Dv FP_INFINITE
Indicates that
.Va x
is an infinite number.
.It Dv FP_NAN
Indicates that
.Va x
is not a number (NaN).
.It Dv FP_NORMAL
Indicates that
.Va x
is a normalized number.
.It Dv FP_SUBNORMAL
Indicates that
.Va x
is a denormalized number.
.It Dv FP_ZERO
Indicates that
.Va x
is zero (0 or -0).
.El
.Pp
The
.Fn isfinite
macro returns a non-zero value if and only if its argument has
a finite (zero, subnormal, or normal) value.  The
.Fn isinf ,
.Fn isnan ,
and
.Fn isnormal
macros return non-zero if and only if
.Va x
is an infinity, NaN,
or a non-zero normalized number, respectively.
.Pp
The symbol
.Fn isnanf
is provided as an alias to
.Fn isnan
for compatibility, and its use is deprecated.
.Sh SEE ALSO
.Xr isgreater 3 ,
.Xr math 3 ,
.Xr signbit 3
.Sh STANDARDS
The
.Fn fpclassify ,
.Fn isfinite ,
.Fn isinf ,
.Fn isnan ,
and
.Fn isnormal
macros conform to
.St -isoC-99 .
.Sh HISTORY
The
.Fn fpclassify ,
.Fn isfinite ,
.Fn isinf ,
.Fn isnan ,
and
.Fn isnormal
macros were added in
.Fx 5.1 .
.Bx 3
introduced
.Fn isinf
and
.Fn isnan
functions, which accepted
.Ft double
arguments; these have been superseded by the macros
described above.
.Sh BUGS
By default, the DEC Alpha architecture does not support IEEE rounding.
See the compiler documentation for additional details.