qpms/qpms/tiny_inlines.h

#ifndef TINY_INLINES_H
#define TINY_INLINES_H
#include <stdlib.h>

static inline int min1pow(int pow) { return (pow % 2) ? -1 : 1; }


// This is useful for calculating spherical harmonics with negative m
// if spharm-normalised legendre functions for positive m are available.
static inline int min1pow_m_neg(int m) {
	return (m < 0) ? min1pow(m) : 1;
}

// this has shitty precision:
// static inline complex double ipow(int x) { return cpow(I, x); }

static inline complex double ipow(int x) {
  x = ((x % 4) + 4) % 4;
  switch(x) {
    case 0:
      return 1;
    case 1:
      return I;
    case 2:
      return -1;
    case 3:
      return -I;
    default:
      abort();
  }
}

#endif // TINY_INLINES_H