;
; iron_combinatorics.hsp — 順列・組み合わせ
;
#ifndef __iron_combinatorics_hsp__
#define __iron_combinatorics_hsp__
#module iron_combinatorics

#defcfunc factorial int n, local r
	r = 1
	repeat n, 1 : r *= cnt : loop
	return r

#defcfunc combination int n, int r
	if r > n : return 0
	return factorial(n) / (factorial(r) * factorial(n - r))

#defcfunc permutation int n, int r
	if r > n : return 0
	return factorial(n) / factorial(n - r)

; GCD (Euclidean algorithm)
#defcfunc gcd int a, int b, local t, local _a, local _b
	_a = a : _b = b
	if _a < 0 : _a = -_a
	if _b < 0 : _b = -_b
	repeat
		if _b == 0 : break
		t = _b : _b = _a \ _b : _a = t
	loop
	return _a

; LCM
#defcfunc lcm int a, int b
	if a == 0 | b == 0 : return 0
	return (a / gcd(a, b)) * b

; Is prime
#defcfunc is_prime int n, local i
	if n < 2 : return 0
	if n < 4 : return 1
	if (n \ 2) == 0 : return 0
	i = 3
	repeat
		if i * i > n : break
		if (n \ i) == 0 : return 0
		i += 2
	loop
	return 1

#global
#endif