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1 | .\" Copyright 2004 Andries Brouwer <aeb@cwi.nl>. |
| 2 | .\" | |
| 3 | .\" Permission is granted to make and distribute verbatim copies of this | |
| 4 | .\" manual provided the copyright notice and this permission notice are | |
| 5 | .\" preserved on all copies. | |
| 6 | .\" | |
| 7 | .\" Permission is granted to copy and distribute modified versions of this | |
| 8 | .\" manual under the conditions for verbatim copying, provided that the | |
| 9 | .\" entire resulting derived work is distributed under the terms of a | |
| 10 | .\" permission notice identical to this one. | |
| c13182ef | 11 | .\" |
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12 | .\" Since the Linux kernel and libraries are constantly changing, this |
| 13 | .\" manual page may be incorrect or out-of-date. The author(s) assume no | |
| 14 | .\" responsibility for errors or omissions, or for damages resulting from | |
| 15 | .\" the use of the information contained herein. The author(s) may not | |
| 16 | .\" have taken the same level of care in the production of this manual, | |
| 17 | .\" which is licensed free of charge, as they might when working | |
| 18 | .\" professionally. | |
| c13182ef | 19 | .\" |
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20 | .\" Formatted or processed versions of this manual, if unaccompanied by |
| 21 | .\" the source, must acknowledge the copyright and authors of this work. | |
| 22 | .\" | |
| 23 | .TH INFINITY 3 2004-10-31 "" "Linux Programmer's Manual" | |
| 24 | .SH NAME | |
| c65433e6 | 25 | INFINITY, NAN, HUGE_VAL, HUGE_VALF, HUGE_VALL \- floating point constants |
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26 | .SH SYNOPSIS |
| 27 | .nf | |
| 28 | #define _ISOC99_SOURCE | |
| 29 | .br | |
| 30 | .B #include <math.h> | |
| 31 | .sp | |
| 32 | .B INFINITY | |
| 33 | .sp | |
| 34 | .B NAN | |
| 35 | .sp | |
| 36 | .B HUGE_VAL | |
| 37 | .br | |
| 38 | .B HUGE_VALF | |
| 39 | .br | |
| 40 | .B HUGE_VALL | |
| 41 | .fi | |
| 42 | .SH DESCRIPTION | |
| 43 | The macro | |
| 44 | .B INFINITY | |
| 45 | expands to a float constant representing positive infinity. | |
| 46 | ||
| 47 | The macro | |
| 48 | .B NAN | |
| 49 | expands to a float constant representing a quiet NaN | |
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50 | (when supported). |
| 51 | A | |
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52 | .I quiet |
| 53 | NaN is a NaN ("not-a-number") that does not raise exceptions | |
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54 | when it is used in arithmetic. |
| 55 | The opposite is a | |
| d9bfdb9c | 56 | .I signaling |
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57 | NaN. |
| 58 | See IEC 60559:1989. | |
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59 | |
| 60 | The macros | |
| 61 | .BR HUGE_VAL , | |
| 62 | .BR HUGE_VALF , | |
| 63 | .BR HUGE_VALL | |
| 64 | expand to constants of types double, float and long double, respectively, | |
| 65 | that represent a large positive value, possibly plus infinity. | |
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66 | .SH "CONFORMING TO" |
| 67 | C99 | |
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68 | .SH AVAILABILITY |
| 69 | On a glibc system, the macro HUGE_VAL is always available. | |
| 70 | Availability of the NAN macro can be tested using | |
| 71 | .BR "#ifdef NAN" , | |
| 72 | and similarly for INFINITY, HUGE_VALF, HUGE_VALL. | |
| 73 | They will be defined by | |
| 74 | .I <math.h> | |
| 75 | if _ISOC99_SOURCE or _GNU_SOURCE is defined, or __STDC_VERSION__ is defined | |
| 76 | and has a value not less than 199901L. | |
| fea681da | 77 | .SH "SEE ALSO" |
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78 | .BR fpclassify (3), |
| 79 | .BR feature_test_macros (7) |