;
; iron_random_dist.hsp — 確率分布乱数生成
;
#ifndef __iron_random_dist_hsp__
#define __iron_random_dist_hsp__
#module iron_random_dist

; Box-Muller transform: generate normal distribution
#defcfunc rand_normal double mean, double stddev, local u1, local u2
	u1 = (double(rnd(10000)) + 1.0) / 10001.0
	u2 = double(rnd(10000)) / 10000.0
	return mean + stddev * sqrt(-2.0 * logf(u1)) * cos(6.28318 * u2)

; Exponential distribution
#defcfunc rand_exponential double lambda
	return -logf((double(rnd(10000)) + 1.0) / 10001.0) / lambda

; Poisson distribution (for small lambda)
#defcfunc rand_poisson double lambda, local L, local k, local p
	L = expf(-lambda)
	k = 0 : p = 1.0
	repeat
		k++
		p *= double(rnd(10000)) / 10000.0
		if p <= L : break
	loop
	return k - 1

; Uniform float [min, max)
#defcfunc rand_uniform double vmin, double vmax
	return vmin + (vmax - vmin) * double(rnd(10000)) / 10000.0

#global
#endif