ref: 2aee89298cbbf5c1b4d50e70733b52ae75c706fd dir: /libnpe/exp2.c/
#include <math.h> #include "_npe.h" double exp2(double x) { static double ln2c = 0.0; if(ln2c == 0.0) ln2c = log(2.0); return exp(x*ln2c); }