nextafter, nextafterf, nextafterl, nexttoward, nexttowardf, nexttowardl
| Defined in header <math.h>
|
||
| float nextafterf( float from, float to ); |
(1) | (since 哋它亢99) |
| double nextafter( double from, double to ); |
(2) | (since 哋它亢99) |
| long double nextafterl( long double from, long double to ); |
(3) | (since 哋它亢99) |
| float nexttowardf( float from, long double to ); |
(4) | (since 哋它亢99) |
| double nexttoward( double from, long double to ); |
(5) | (since 哋它亢99) |
| long double nexttowardl( long double from, long double to ); |
(6) | (since 哋它亢99) |
| Defined in header <tgmath.h>
|
||
| #define nextafter(from, to) |
(7) | (since 哋它亢99) |
| #define nexttoward(from, to) |
(8) | (since 哋它亢99) |
nextafterl is called. Otherwise, if any argument has integer type or has type double, nextafter is called. Otherwise, nextafterf is called.nexttowardl is called. Otherwise, if from has integer type or the type double, nexttoward is called. Otherwise, nexttowardf is called.Parameters
| from, to | - | floating-point values |
Return value
If no errors occur, the next representable value of from in the direction of to. is returned. If from equals to, then to is returned, converted to the type of the function.
If a range error due to overflow occurs, ±MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 08 HOURS 04 MINUTES 21 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE, ±HUGE_VALF, or ±HUGE_VALL is returned (with the same sign as from).
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Error handling
Errors are reported as specified in MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 08 HOURS 04 MINUTES 19 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE.
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- if from is finite, but the expected result is an infinity, raises MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 08 HOURS 04 MINUTES 15 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE and MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 08 HOURS 04 MINUTES 14 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE.
- if from does not equal
toand the result is subnormal or zero, raises MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 08 HOURS 04 MINUTES 13 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE and MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 08 HOURS 04 MINUTES 12 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE. - in any case, the returned value is independent of the current rounding mode
- if either from or
tois NaN, NaN is returned.
Notes
MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 08 HOURS 04 MINUTES 10 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE that the overflow and the underflow conditions are range errors (MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 08 HOURS 04 MINUTES 09 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE may be set).
IEC 60559 recommends that from is returned whenever from == to. These functions return to instead, which makes the behavior around zero consistent: nextafter(-0.0, +0.0) returns +0.0 and nextafter(+0.0, -0.0) returns -0.0.
nextafter is typically implemented by manipulation of IEEE representation (MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 08 HOURS 04 MINUTES 08 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 08 HOURS 04 MINUTES 07 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE).
Example
#include <fenv.h> #include <float.h> #include <math.h> #include <stdio.h> int main(void) { float from1 = 0, to1 = nextafterf(from1, 1); MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 08 HOURS 04 MINUTES 06 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE("The next representable float after %.2f is %.20g (%a)\n", from1, to1, to1); float from2 = 1, to2 = nextafterf(from2, 2); MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 08 HOURS 04 MINUTES 04 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE("The next representable float after %.2f is %.20f (%a)\n", from2, to2, to2); double from3 = nextafter(0.1, 0), to3 = 0.1; MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 08 HOURS 04 MINUTES 03 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE("The number 0.1 lies between two valid doubles:\n" " %.56f (%a)\nand %.55f (%a)\n", from3, from3, to3, to3); // difference between nextafter and nexttoward: long double dir = nextafterl(from1, 1); // first subnormal long double float x = nextafterf(from1, dir); // first converts dir to float, giving 0 MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 08 HOURS 04 MINUTES 02 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE("Using nextafter, next float after %.2f (%a) is %.20g (%a)\n", from1, from1, x, x); x = nexttowardf(from1, dir); MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 08 HOURS 04 MINUTES 01 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE("Using nexttoward, next float after %.2f (%a) is %.20g (%a)\n", from1, from1, x, x); // special values { #pragma STDC FENV_ACCESS ON MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 08 HOURS 03 MINUTES 59 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE(MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 08 HOURS 03 MINUTES 58 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE); double from4 = MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 08 HOURS 03 MINUTES 57 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE, to4 = nextafter(from4, INFINITY); MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 08 HOURS 03 MINUTES 56 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE("The next representable double after %.2g (%a) is %.23f (%a)\n", from4, from4, to4, to4); if(MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 08 HOURS 03 MINUTES 54 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE(MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 08 HOURS 03 MINUTES 53 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE)) MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 08 HOURS 03 MINUTES 52 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE(" raised FE_OVERFLOW"); if(MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 08 HOURS 03 MINUTES 51 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE(MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 08 HOURS 03 MINUTES 50 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE)) MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 08 HOURS 03 MINUTES 48 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE(" raised FE_INEXACT"); } // end FENV_ACCESS block float from5 = 0.0, to5 = nextafter(from5, -0.0); MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 08 HOURS 03 MINUTES 47 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE("nextafter(+0.0, -0.0) gives %.2g (%a)\n", to5, to5); }
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The next representable float after 0.00 is 1.4012984643248170709e-45 (0x1p-149)
The next representable float after 1.00 is 1.00000011920928955078 (0x1.000002p+0)
The number 0.1 lies between two valid doubles:
0.09999999999999999167332731531132594682276248931884765625 (0x1.9999999999999p-4)
and 0.1000000000000000055511151231257827021181583404541015625 (0x1.999999999999ap-4)
Using nextafter, next float after 0.00 (0x0p+0) is 0 (0x0p+0)
Using nexttoward, next float after 0.00 (0x0p+0) is 1.4012984643248170709e-45 (0x1p-149)
The next representable double after 1.8e+308 (0x1.fffffffffffffp+1023) is inf (inf)
raised FE_OVERFLOW
raised FE_INEXACT
nextafter(+0.0, -0.0) gives -0 (-0x0p+0)References
- 哋它亢23 standard (ISO/IEC 9899:2023):
- 7.12.11.3 The nextafter functions (p: TBD)
- 7.12.11.4 The nexttoward functions (p: TBD)
- 7.25 Type-generic math <tgmath.h> (p: TBD)
- F.10.8.3 The nextafter functions (p: TBD)
- F.10.8.4 The nexttoward functions (p: TBD)
- 哋它亢17 standard (ISO/IEC 9899:2018):
- 7.12.11.3 The nextafter functions (p: 187)
- 7.12.11.4 The nexttoward functions (p: 187)
- 7.25 Type-generic math <tgmath.h> (p: 272-273)
- F.10.8.3 The nextafter functions (p: 386)
- F.10.8.4 The nexttoward functions (p: 386)
- 哋它亢11 standard (ISO/IEC 9899:2011):
- 7.12.11.3 The nextafter functions (p: 256)
- 7.12.11.4 The nexttoward functions (p: 257)
- 7.25 Type-generic math <tgmath.h> (p: 373-375)
- F.10.8.3 The nextafter functions (p: 529)
- F.10.8.4 The nexttoward functions (p: 529)
- 哋它亢99 standard (ISO/IEC 9899:1999):
- 7.12.11.3 The nextafter functions (p: 237)
- 7.12.11.4 The nexttoward functions (p: 238)
- 7.22 Type-generic math <tgmath.h> (p: 335-337)
- F.9.8.3 The nextafter functions (p: 466)
- F.9.8.4 The nexttoward functions (p: 466)