mirror of https://github.com/mkerrisk/man-pages
112 lines
3.6 KiB
Plaintext
112 lines
3.6 KiB
Plaintext
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.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
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.TH "FDIM" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
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.\" fdim
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.SH NAME
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fdim, fdimf, fdiml \- compute positive difference between two floating-point
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numbers
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.SH SYNOPSIS
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.LP
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\fB#include <math.h>
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.br
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.sp
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double fdim(double\fP \fIx\fP\fB, double\fP \fIy\fP\fB);
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.br
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float fdimf(float\fP \fIx\fP\fB, float\fP \fIy\fP\fB);
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.br
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long double fdiml(long double\fP \fIx\fP\fB, long double\fP \fIy\fP\fB);
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.br
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\fP
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.SH DESCRIPTION
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.LP
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These functions shall determine the positive difference between their
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arguments. If \fIx\fP is greater than \fIy\fP, \fIx\fP-
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\fIy\fP is returned. If \fIx\fP is less than or equal to \fIy\fP,
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+0 is returned.
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.LP
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An application wishing to check for error situations should set \fIerrno\fP
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to zero and call
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\fIfeclearexcept\fP(FE_ALL_EXCEPT) before calling these functions.
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On return, if \fIerrno\fP is non-zero or
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\fIfetestexcept\fP(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW)
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is non-zero, an error has occurred.
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.SH RETURN VALUE
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.LP
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Upon successful completion, these functions shall return the positive
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difference value.
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.LP
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If \fIx\fP- \fIy\fP is positive and overflows, a range error shall
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occur and \fIfdim\fP(), \fIfdimf\fP(), and \fIfdiml\fP()
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shall return the value of the macro HUGE_VAL, HUGE_VALF, and HUGE_VALL,
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respectively.
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.LP
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If \fIx\fP- \fIy\fP is positive and underflows, a range error may
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occur, and either ( \fIx\fP- \fIy\fP) (if representable),
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\ or 0.0 (if supported), or an implementation-defined value
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shall be returned.
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.LP
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If
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\fIx\fP or \fIy\fP is NaN, a NaN shall be returned.
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.SH ERRORS
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.LP
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The \fIfdim\fP() function shall fail if:
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.TP 7
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Range\ Error
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The result overflows.
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.LP
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If the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
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then \fIerrno\fP shall be set to [ERANGE]. If the
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integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero,
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then the overflow floating-point exception shall be
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raised.
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.sp
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.LP
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The \fIfdim\fP() function may fail if:
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.TP 7
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Range\ Error
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The result underflows.
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.LP
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If the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
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then \fIerrno\fP shall be set to [ERANGE]. If the
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integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero,
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then the underflow floating-point exception shall be
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raised.
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.sp
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.LP
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\fIThe following sections are informative.\fP
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.SH EXAMPLES
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.LP
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None.
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.SH APPLICATION USAGE
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.LP
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On implementations supporting IEEE\ Std\ 754-1985, \fIx\fP- \fIy\fP
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cannot underflow, and hence the 0.0 return value
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is shaded as an extension for implementations supporting the XSI extension
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rather than an MX extension.
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.LP
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On error, the expressions (math_errhandling & MATH_ERRNO) and (math_errhandling
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& MATH_ERREXCEPT) are independent of
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each other, but at least one of them must be non-zero.
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.SH RATIONALE
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.LP
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None.
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.SH FUTURE DIRECTIONS
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.LP
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None.
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.SH SEE ALSO
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.LP
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\fIfeclearexcept\fP() , \fIfetestexcept\fP() , \fIfmax\fP() , \fIfmin\fP()
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, the Base Definitions volume of
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IEEE\ Std\ 1003.1-2001, Section 4.18, Treatment of Error Conditions
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for
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Mathematical Functions, \fI<math.h>\fP
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.SH COPYRIGHT
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Portions of this text are reprinted and reproduced in electronic form
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from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
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-- Portable Operating System Interface (POSIX), The Open Group Base
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Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
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Electrical and Electronics Engineers, Inc and The Open Group. In the
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event of any discrepancy between this version and the original IEEE and
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The Open Group Standard, the original IEEE and The Open Group Standard
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is the referee document. The original Standard can be obtained online at
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http://www.opengroup.org/unix/online.html .
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