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| .TH INFINITY 3 2020-06-09 "" "Linux Programmer's Manual" |
| .SH NAME |
| INFINITY, NAN, HUGE_VAL, HUGE_VALF, HUGE_VALL \- floating-point constants |
| .SH SYNOPSIS |
| .nf |
| .BR "#define _ISOC99_SOURCE" " /* See feature_test_macros(7) */" |
| .B #include <math.h> |
| .PP |
| .B INFINITY |
| .PP |
| .B NAN |
| .PP |
| .B HUGE_VAL |
| .B HUGE_VALF |
| .B HUGE_VALL |
| .fi |
| .SH DESCRIPTION |
| The macro |
| .B INFINITY |
| expands to a |
| .I float |
| constant representing positive infinity. |
| .PP |
| The macro |
| .B NAN |
| expands to a |
| .I 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 signaling |
| NaN. |
| See IEC 60559:1989. |
| .PP |
| The macros |
| .BR HUGE_VAL , |
| .BR HUGE_VALF , |
| .B HUGE_VALL |
| expand to constants of types |
| .IR double , |
| .I float |
| and |
| .IR "long double" , |
| respectively, |
| that represent a large positive value, possibly positive infinity. |
| .SH CONFORMING TO |
| C99. |
| .PP |
| On a glibc system, the macro |
| .B HUGE_VAL |
| is always available. |
| Availability of the |
| .B NAN |
| macro can be tested using |
| .BR "#ifdef NAN" , |
| and similarly for |
| .BR INFINITY , |
| .BR HUGE_VALF , |
| .BR HUGE_VALL . |
| They will be defined by |
| .I <math.h> |
| if |
| .B _ISOC99_SOURCE |
| or |
| .B _GNU_SOURCE |
| is defined, or |
| .B __STDC_VERSION__ |
| is defined |
| and has a value not less than 199901L. |
| .SH SEE ALSO |
| .BR fpclassify (3), |
| .BR math_error (7) |