# exp2, exp2f, exp2l

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< c‎ | numeric‎ | math

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.

### Parameters

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

### Example

Run this code

    #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");
    }

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

### References

- C11 standard (ISO/IEC 9899:2011):

  - 7.12.6.2 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):

  - 7.12.6.2 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

exp expf expl (C99)(C99) | computes e raised to the given power (ex) (function)
expm1 expm1f expm1l (C99)(C99)(C99) | computes e raised to the given power, minus one (ex-1) (function)
log2 log2f log2l (C99)(C99)(C99) | computes base-2 logarithm (log2(x)) (function)

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