exp2

static assert(real.nan.exp2.isNaN);
static assert(real.infinity.exp2.isInfinity);
static assert((-real.infinity).exp2 == 0);
static assert(0.exp2 == 1);
static assert(2.exp2 == 4);
static assert(8.exp2 == 256);
static assert((-1).exp2 == 0.5);