Approximate e^x

Question

I\'d like to approximate the e^x function.

Is it possible to do so using multiple splines type based approach? i.e between x₁

Answer 1

This is not the smooth spline interpolation you requested but its computationally efficient:

float expf_fast(float x) {
   union { float f; int i; } y;
   y.i = (int)(x * 0xB5645F + 0x3F7893F5);
   return (y.f);
}

Plot Output