Legacy Document

exp2

You can use the exp2 function to raise 2 to some power.

double_t exp2 (double_t x);

x

Any floating-point number.

DESCRIPTION

The exp2 function returns the base 2 exponential of its argument.

$exp2(x)\; =\; 2x$

The log2 function performs the inverse operation $log$₂2^x) .

EXCEPTIONS

When x is finite and nonzero, the result of $exp2(x)$ might raise the following exceptions:

• inexact (for all finite, nonzero values of x)
• overflow (if the result is outside the range of the data type)
• underflow (if the result is inexact and must be represented as a denormalized number or 0)

SPECIAL CASES

Table 10-8 shows the results when the argument to the exp2 function is a zero, a NaN, or an Infinity.

Special cases for the exp2 function

Operation	Result	Exceptions raised
$exp2(+0)$	+1	None
$exp2(-0)$	+1	None
$exp2(NaN)$	NaN	None[29]
$exp2(+$ )	+	None
$exp2(-$ )	+0	None

EXAMPLES

z = exp2(2.0); /* z = 22 = 4. The inexact exception is raised. */
z = exp2(1.5); /* z = 21.5  2.82843. The inexact exception is 
                  raised. */

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[29] If the NaN is a signaling NaN, the invalid exception is raised.