frexp.3

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· 3 代码 · 共 66 行

.\" SCCSID: @(#)frexp.3	6.3	8/30/89
.TH frexp 3
.SH Name
frexp, ldexp, modf \- split into mantissa and exponent
.SH Syntax
.nf
.B #include <math.h>
.PP
.B double frexp(\fIvalue, eptr\fP)
.B double \fIvalue\fP;
.B int *\fIeptr\fP;
.PP
.B double ldexp(\fIvalue, exp\fP)
.B double \fIvalue\fP;
.PP
.B double modf(\fIvalue, iptr\fP)
.B double \fIvalue, *iptr\fP;
.SH Description
.NXR "frexp subroutine"
.NXR "ldexp subroutine"
.NXR "modf subroutine"
.NXR "mantissa" "splitting into"
.NXR "exponent" "splitting into"
The
.PN frexp
subroutine
returns the mantissa of a double 
.I value
as a double quantity,
.I x,
of magnitude less than 1.0 and greater than or equal to
0.5 (0.5 <= |x| < 1) and stores an integer 
.I n
such that
.I value
=
\fIx\fP*2**\fIn\fP
indirectly through 
.I eptr.
.PP
The
.PN ldexp
returns the quantity
\fIvalue*2**\fIexp\fP.
.PP
The
.PN modf
returns the positive fractional part of
.I value
and stores the integer part indirectly
through 
.I iptr.
.SH Return Values
If 
.PN ldexp
would cause overflow, \(+-HUGE_VAL
is returned (according to the sign of
.IR value )
and
.I errno
is set to ERANGE.  If
.PN ldexp
would cause underflow, 0 is returned and
.I errno
is set to ERANGE.