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.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 

.TH "FDIM" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"

.\" fdim 

.SH NAME

fdim, fdimf, fdiml \- compute positive difference between two floating-point

numbers

.SH SYNOPSIS

.LP

\fB#include <math.h>

.br

.sp

double fdim(double\fP \fIx\fP\fB, double\fP \fIy\fP\fB);

.br

float fdimf(float\fP \fIx\fP\fB, float\fP \fIy\fP\fB);

.br

long double fdiml(long double\fP \fIx\fP\fB, long double\fP \fIy\fP\fB);

.br

\fP

.SH DESCRIPTION

.LP

These functions shall determine the positive difference between their

arguments. If \fIx\fP is greater than \fIy\fP, \fIx\fP-

\fIy\fP is returned. If \fIx\fP is less than or equal to \fIy\fP,

+0 is returned.

.LP

An application wishing to check for error situations should set \fIerrno\fP

to zero and call

\fIfeclearexcept\fP(FE_ALL_EXCEPT) before calling these functions.

On return, if \fIerrno\fP is non-zero or

\fIfetestexcept\fP(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW)

is non-zero, an error has occurred.

.SH RETURN VALUE

.LP

Upon successful completion, these functions shall return the positive

difference value.

.LP

If \fIx\fP- \fIy\fP is positive and overflows, a range error shall

occur and \fIfdim\fP(), \fIfdimf\fP(), and \fIfdiml\fP()

shall return the value of the macro HUGE_VAL, HUGE_VALF, and HUGE_VALL,

respectively.

.LP

If \fIx\fP- \fIy\fP is positive and underflows, a range error may

occur, and either ( \fIx\fP- \fIy\fP) (if representable),

\ or 0.0 (if supported),  or an implementation-defined value

shall be returned.

.LP

If

\fIx\fP or \fIy\fP is NaN, a NaN shall be returned. 

.SH ERRORS

.LP

The \fIfdim\fP() function shall fail if:

.TP 7

Range\ Error

The result overflows. 

.LP

If the integer expression (math_errhandling & MATH_ERRNO) is non-zero,

then \fIerrno\fP shall be set to [ERANGE]. If the

integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero,

then the overflow floating-point exception shall be

raised.

.sp

.LP

The \fIfdim\fP() function may fail if:

.TP 7

Range\ Error

The result underflows. 

.LP

If the integer expression (math_errhandling & MATH_ERRNO) is non-zero,

then \fIerrno\fP shall be set to [ERANGE]. If the

integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero,

then the underflow floating-point exception shall be

raised.

.sp

.LP

\fIThe following sections are informative.\fP

.SH EXAMPLES

.LP

None.

.SH APPLICATION USAGE

.LP

On implementations supporting IEEE\ Std\ 754-1985, \fIx\fP- \fIy\fP

cannot underflow, and hence the 0.0 return value

is shaded as an extension for implementations supporting the XSI extension

rather than an MX extension.

.LP

On error, the expressions (math_errhandling & MATH_ERRNO) and (math_errhandling

& MATH_ERREXCEPT) are independent of

each other, but at least one of them must be non-zero.

.SH RATIONALE

.LP

None.

.SH FUTURE DIRECTIONS

.LP

None.

.SH SEE ALSO

.LP

\fIfeclearexcept\fP() , \fIfetestexcept\fP() , \fIfmax\fP() , \fIfmin\fP()

, the Base Definitions volume of

IEEE\ Std\ 1003.1-2001, Section 4.18, Treatment of Error Conditions

for

Mathematical Functions, \fI<math.h>\fP

.SH COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form

from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology

-- Portable Operating System Interface (POSIX), The Open Group Base

Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of

Electrical and Electronics Engineers, Inc and The Open Group. In the

event of any discrepancy between this version and the original IEEE and

The Open Group Standard, the original IEEE and The Open Group Standard

is the referee document. The original Standard can be obtained online at

http://www.opengroup.org/unix/online.html .