| .\" Copyright 2004 Andries Brouwer <aeb@cwi.nl>. |
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| .TH INFINITY 3 2004-10-31 "" "Linux Programmer's Manual" |
| .SH NAME |
| INFINITY, NAN, HUGE_VAL, HUGE_VALF, HUGE_VALL \- floating point constants |
| .SH SYNOPSIS |
| .nf |
| #define _ISOC99_SOURCE |
| .br |
| .B #include <math.h> |
| .sp |
| .B INFINITY |
| .sp |
| .B NAN |
| .sp |
| .B HUGE_VAL |
| .br |
| .B HUGE_VALF |
| .br |
| .B HUGE_VALL |
| .fi |
| .SH DESCRIPTION |
| The macro |
| .B INFINITY |
| expands to a float constant representing positive infinity. |
| |
| The macro |
| .B NAN |
| expands to a float constant representing a quiet NaN |
| (when supported). A |
| .I quiet |
| NaN is a NaN ("not-a-number") that does not raise exceptions |
| when it is used in arithmetic. The opposite is a |
| .I signalling |
| NaN. See IEC 60559:1989. |
| |
| The macros |
| .BR HUGE_VAL , |
| .BR HUGE_VALF , |
| .BR HUGE_VALL |
| expand to constants of types double, float and long double, respectively, |
| that represent a large positive value, possibly plus infinity. |
| |
| .SH AVAILABILITY |
| On a glibc system, the macro HUGE_VAL is always available. |
| Availability of the NAN macro can be tested using |
| .BR "#ifdef NAN" , |
| and similarly for INFINITY, HUGE_VALF, HUGE_VALL. |
| They will be defined by |
| .I <math.h> |
| if _ISOC99_SOURCE or _GNU_SOURCE is defined, or __STDC_VERSION__ is defined |
| and has a value not less than 199901L. |
| |
| .SH "CONFORMING TO" |
| C99 |
| .SH "SEE ALSO" |
| .BR fpclassify (3) |