| Pré. | Proc. |
exp2
Base 2 exponential function.SYNOPSIS:
double x, y, exp2();
y = exp2(x);
DESCRIPTION:
Returns 2 raised to the x power.
Range reduction is accomplished by separating the argument into an integer k and fraction f, such that:
x k f
2 = 2 2
A Pade' form:
1 + 2x P(x**2) / (Q(x**2) - x P(x**2))
approximates 2**x in the basic range [-0.5, 0.5].
ACCURACY:
Relative error:
arithmetic domain # trials peak rms
IEEE -1022,+1024 30000 1.8e-16 5.4e-17
ERROR MESSAGES:
message condition value returned
underflow x < -MAXL2 0.0
overflow x > MAXL2 MAXNUM
For DEC arithmetic, MAXL2 = 127.
For IEEE arithmetic, MAXL2 = 1024.