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在頭文件<math.h>中定義 | ||
---|---|---|
float rintf( float arg ); | (1) | (since C99) |
double rint( double arg ); | (2) | (since C99) |
long double rintl( long double arg ); | (3) | (since C99) |
Defined in header <tgmath.h> | ||
#define rint( arg ) | (4) | (since C99) |
Defined in header <math.h> | ||
long lrintf( float arg ); | (5) | (since C99) |
long lrint( double arg ); | (6) | (since C99) |
long lrintl( long double arg ); | (7) | (since C99) |
Defined in header <tgmath.h> | ||
#define lrint( arg ) | (8) | (since C99) |
Defined in header <math.h> | ||
long long llrintf( float arg ); | (9) | (since C99) |
long long llrint( double arg ); | (10) | (since C99) |
long long llrintl( long double arg ); | (11) | (since C99) |
Defined in header <tgmath.h> | ||
#define llrint( arg ) | (12) | (since C99) |
1-3)arg
使用當(dāng)前舍入模式將浮點(diǎn)參數(shù)四舍五入為浮點(diǎn)格式的整數(shù)值。
5-7,9-11)arg
使用當(dāng)前舍入模式將浮點(diǎn)參數(shù)四舍五入為整數(shù)格式的整數(shù)值。
4,8,12)類型泛型宏:如果arg
有一個(gè)類型long double
,rintl
,lrintl
,llrintl
被調(diào)用。否則,如果arg
有整數(shù)類型或類型double
,rint
,lrint
,llrint
被調(diào)用。否則rintf
,lrintf
,llrintf
叫,分別。
arg | - | 浮點(diǎn)值 |
---|
如果沒有發(fā)生錯(cuò)誤,則返回arg
根據(jù)當(dāng)前舍入模式最接近的整數(shù)值。
按照math_errhandling中的指定報(bào)告錯(cuò)誤。
如果返回類型表示的范圍lrint
或結(jié)果llrint
超出范圍,則可能會(huì)出現(xiàn)域錯(cuò)誤或范圍錯(cuò)誤。
如果實(shí)現(xiàn)支持IEEE浮點(diǎn)運(yùn)算(IEC 60559),則對(duì)于rint
函數(shù):
如果arg
是±∞,則返回,未修改
如果arg
為±0,則返回,未修改
如果arg
是NaN,則返回NaN
為lrint
和llrint
功能:
如果arg
是±∞,FE_INVALID
則引發(fā)并返回實(shí)現(xiàn)定義的值
如果舍入的結(jié)果超出返回類型的范圍,FE_INVALID
則會(huì)引發(fā)并返回實(shí)現(xiàn)定義的值
如果arg
是NaN,FE_INVALID
則引發(fā)并返回實(shí)現(xiàn)定義的值
POSIX規(guī)定是,所有病例lrint
或llrint
提高FE_INEXACT
是域錯(cuò)誤。
如math_errhandling中指定的,FE_INEXACT
可能(但不要求在非IEEE浮點(diǎn)平臺(tái)上)rint
在舍入非整數(shù)有限值時(shí)引發(fā)。
之間唯一的區(qū)別rint
和nearbyint
是nearbyint
永遠(yuǎn)不會(huì)提高FE_INEXACT
。
最大的可表示浮點(diǎn)值是所有標(biāo)準(zhǔn)浮點(diǎn)格式中的精確整數(shù),因此rint
不會(huì)自行溢出; 但是intmax_t
,當(dāng)存儲(chǔ)在整數(shù)變量中時(shí),結(jié)果可能會(huì)溢出任何整數(shù)類型(包括)。
如果當(dāng)前舍入模式是...
FE_DOWNWARD
,那么rint
相當(dāng)于floor
。
FE_UPWARD
,那么rint
相當(dāng)于ceil
。
FE_TOWARDZERO
,那么rint
相當(dāng)于trunc
FE_TONEAREST
,rint
不同之處round
在于中途情況被舍入到甚至遠(yuǎn)離零。
#include <stdio.h>#include <math.h>#include <fenv.h>#include <limits.h> int main(void){#pragma STDC FENV_ACCESS ON fesetround(FE_TONEAREST); printf("rounding to nearest (halfway cases to even):\n" "rint(+2.3) = %+.1f ", rint(2.3)); printf("rint(+2.5) = %+.1f ", rint(2.5)); printf("rint(+3.5) = %+.1f\n", rint(3.5)); printf("rint(-2.3) = %+.1f ", rint(-2.3)); printf("rint(-2.5) = %+.1f ", rint(-2.5)); printf("rint(-3.5) = %+.1f\n", rint(-3.5)); fesetround(FE_DOWNWARD); printf("rounding down: \nrint(+2.3) = %+.1f ", rint(2.3)); printf("rint(+2.5) = %+.1f ", rint(2.5)); printf("rint(+3.5) = %+.1f\n", rint(3.5)); printf("rint(-2.3) = %+.1f ", rint(-2.3)); printf("rint(-2.5) = %+.1f ", rint(-2.5)); printf("rint(-3.5) = %+.1f\n", rint(-3.5)); printf("rounding down with lrint: \nlrint(+2.3) = %ld ", lrint(2.3)); printf("lrint(+2.5) = %ld ", lrint(2.5)); printf("lrint(+3.5) = %ld\n", lrint(3.5)); printf("lrint(-2.3) = %ld ", lrint(-2.3)); printf("lrint(-2.5) = %ld ", lrint(-2.5)); printf("lrint(-3.5) = %ld\n", lrint(-3.5)); printf("lrint(-0.0) = %ld\n", lrint(-0.0)); printf("lrint(-Inf) = %ld\n", lrint(-INFINITY)); // FE_INVALID raised // error handling feclearexcept(FE_ALL_EXCEPT); printf("rint(1.1) = %.1f\n", rint(1.1)); if(fetestexcept(FE_INEXACT)) puts(" FE_INEXACT was raised"); feclearexcept(FE_ALL_EXCEPT); printf("lrint(LONG_MIN-2048.0) = %ld\n", lrint(LONG_MIN-2048.0)); if(fetestexcept(FE_INVALID)) puts(" FE_INVALID was raised");}
可能的輸出:
rounding to nearest (halfway cases to even):rint(+2.3) = +2.0 rint(+2.5) = +2.0 rint(+3.5) = +4.0rint(-2.3) = -2.0 rint(-2.5) = -2.0 rint(-3.5) = -4.0rounding down: rint(+2.3) = +2.0 rint(+2.5) = +2.0 rint(+3.5) = +3.0rint(-2.3) = -3.0 rint(-2.5) = -3.0 rint(-3.5) = -4.0rounding down with lrint: lrint(+2.3) = 2 lrint(+2.5) = 2 lrint(+3.5) = 3lrint(-2.3) = -3 lrint(-2.5) = -3 lrint(-3.5) = -4lrint(-0.0) = 0lrint(-Inf) = -9223372036854775808rint(1.1) = 1.0 FE_INEXACT was raisedlrint(LONG_MIN-2048.0) = -9223372036854775808 FE_INVALID was raised
C11標(biāo)準(zhǔn)(ISO / IEC 9899:2011):
7.12.9.4 rint函數(shù)(p:252)
7.12.9.5印刷和印刷功能(p:252)
7.25類型通用數(shù)學(xué)<tgmath.h>(p:373-375)
F.10.6.4 rint函數(shù)(p:527)
F.10.6.5打印和打印功能(p:527)
C99標(biāo)準(zhǔn)(ISO / IEC 9899:1999):
7.12.9.4 rint函數(shù)(p:232-233)
7.12.9.5印刷和印刷功能(p:233)
7.22類型通用數(shù)學(xué)<tgmath.h>(p:335-337)
F.9.6.4 rint函數(shù)(p:463)
F.9.6.5打印和打印功能(p:463)