Evaluates the base 2 exponential function.
input value
function value
var v = exp2( 3.0 ); // returns 8.0
var v = exp2( -9.0 ); // returns ~0.002
var v = exp2( 0.0 ); // returns 1.0
var v = exp2( NaN ); // returns NaN
Evaluates the base 2 exponential function.