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文字

在头文件<math.h>中定义



float exp2f(float n);

(1)

(自C99以来)

double exp2(double n);

(2)

(自C99以来)

long double exp2l(long double n);

(3)

(自C99以来)

在头文件<tgmath.h>中定义



#define exp2(n)

(4)

(自C99以来)

1-3)计算2给定的倍率n。

4)类型通用宏:如果n的类型是long double,则调用exp2l。 否则,如果n具有整数类型或类型double,则调用exp2。 否则,调用exp2f。

参数

n

-

floating point value

返回值

如果没有错误发生,则n的基2指数(2n

)被返回。

如果发生由溢出引起的范围错误,则返回+ HUGE_VAL,+ HUGE_VALF或+ HUGE_VALL。

如果由于下溢而发生范围错误,则返回正确的结果(舍入后)。

错误处理

按照math_errhandling中的指定报告错误。

如果实现支持IEEE浮点运算(IEC 60559),

  • 如果参数是±0,则返回1

  • 如果参数是-∞,则返回+0

  • 如果参数是+∞,则返回+∞

  • 如果参数是NaN,则返回NaN

#include <stdio.h>#include <math.h>#include <float.h>#include <errno.h>#include <fenv.h>#pragma STDC FENV_ACCESS ON
int main(void){    printf("exp2(5) = %f\n", exp2(5));    printf("exp2(0.5) = %f\n", exp2(0.5));    printf("exp2(-4) = %f\n", exp2(-4));    // special values    printf("exp2(-9) = %f\n", exp2(-0.9));    printf("exp2(-Inf) = %f\n", exp2(-INFINITY));    //error handling
    errno = 0; feclearexcept(FE_ALL_EXCEPT);    printf("exp2(1024) = %f\n", exp2(1024));    if(errno == ERANGE) perror("    errno == ERANGE");    if(fetestexcept(FE_OVERFLOW)) puts("    FE_OVERFLOW raised");}

可能的输出:

exp2(5) = 32.000000exp2(0.5) = 1.414214exp2(-4) = 0.062500exp2(-9) = 0.535887exp2(-Inf) = 0.000000exp2(1024) = Inf
    errno == ERANGE: Result too large
    FE_OVERFLOW raised

参考

  • C11标准(ISO / IEC 9899:2011):

    • 7.12.6.2 exp2函数(p:242-243)

    • 7.25类型通用数学<tgmath.h>(p:373-375)

    • F.10.3.2 exp2函数(p:521)

  • C99标准(ISO / IEC 9899:1999):

    • 7.12.6.2 exp2函数(p:223)

    • 7.22类型通用数学<tgmath.h>(p:335-337)

    • F.9.3.2 exp2函数(p:458)

扩展内容

Expexpfexpl(C99)(C99)

计算e给定的倍率(ex)(函数)

expper1expm1fexpm1l(C99)(C99)(C99)

计算e增加到给定的倍率,减去一(ex-1)(函数)

log2log2flog21(C99)(C99)(C99)

计算以2为底的对数(log2(x))(函数)

| exp2的C ++文档 |

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