exp2, exp2f, exp2l

Defined in header <math.h>
float       exp2f( float n );
(1) (since C99)
double      exp2( double n );
(2) (since C99)
long double exp2l( long double n );
(3) (since C99)
Defined in header <tgmath.h>
#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.


n - floating point value

Return value

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.

Error handling

Errors are reported as specified in math_errhandling.

If the implementation supports IEEE floating-point arithmetic (IEC 60559),

  • If the argument is ±0, 1 is returned
  • If the argument is -∞, +0 is returned
  • If the argument is +∞, +∞ is returned
  • If the argument is NaN, NaN is returned


#include <stdio.h>
#include <math.h>
#include <float.h>
#include <errno.h>
#include <fenv.h>
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");

Possible output:

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


  • C11 standard (ISO/IEC 9899:2011):
    • The exp2 functions (p: 242-243)
    • 7.25 Type-generic math <tgmath.h> (p: 373-375)
    • F.10.3.2 The exp2 functions (p: 521)
  • C99 standard (ISO/IEC 9899:1999):
    • The exp2 functions (p: 223)
    • 7.22 Type-generic math <tgmath.h> (p: 335-337)
    • F.9.3.2 The exp2 functions (p: 458)

See also

computes e raised to the given power (ex)
computes e raised to the given power, minus one (ex-1)
computes base-2 logarithm (log2(x))

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