float exp2f( float n );
(1) (since C99)double exp2( double n );
(2) (since C99)long double exp2l( long double n );
(3) (since C99)#define exp2( n )
(4) (since C99)1-3) Computes 2 raised to the given power n.
4) Type-generic macro: If n has type long double, exp2l is called. Otherwise, if n has integer type or the type double, exp2 is called. Otherwise, exp2f is called.
If no errors occur, the base-2 exponential of n (2n
) is returned.
If a range error due to overflow occurs, +HUGE_VAL, +HUGE_VALF, or +HUGE_VALL is returned.
If a range error occurs due to underflow, the correct result (after rounding) is returned.
[edit] Error handlingErrors are reported as specified in math_errhandling.
If the implementation supports IEEE floating-point arithmetic (IEC 60559),
#include <errno.h>
#include <fenv.h>
#include <float.h>
#include <math.h>
#include <stdio.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(-0.9) = %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");
}
Possible output:
exp2(5) = 32.000000
exp2(0.5) = 1.414214
exp2(-4) = 0.062500
exp2(-0.9) = 0.535887
exp2(-Inf) = 0.000000
exp2(1024) = Inf
errno == ERANGE: Result too large
FE_OVERFLOW raised[edit] References
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