/*
PROBABILITY.C

symbols in this file:
000FA5F0 0030:
	_factorial (0000)
000FA620 0030:
	_permutations (0000)
000FA650 0050:
	_combinations (0000)
000FA6A0 00f0:
	_permute (0000)
000FA790 0120:
	_combine (0000)
0027AE48 0008:
	??_C@_07OKCKIPNN@indices?$AA@ (0000)
0027AE50 0007:
	??_C@_06POCLMCPF@base?$DO0?$AA@ (0000)
0027AE58 0022:
	??_C@_0CC@JNAEFKFC@c?3?2halo?2SOURCE?2math?2probability?4@ (0000)
0027AE7C 000c:
	??_C@_0M@EDJJGKEM@base?$DO?$DNcount?$AA@ (0000)
*/

/* ---------- headers */

#include "cseries.h"

/* ---------- constants */

/* ---------- macros */

/* ---------- structures */

/* ---------- prototypes */

/* ---------- globals */

/* ---------- public code */

long factorial(short value)
{
	long result = 0;
	short factor;

	if (value >= 0)
	{
		result = 1;
		for (factor = value; factor > 1; factor--)
		{
			result *= factor;
		}
	}

	return result;
}

long permutations(
	short count,
	short selection_count)
{
	long result = 0;

	if (count >= selection_count && selection_count >= 0)
	{
		result = 1;
		while (selection_count != 0)
		{
			result *= count;
			count--;
			selection_count--;
		}
	}

	return result;
}

long combinations(
	short count,
	short selection_count)
{
	long result = 0;
	short divisor;

	if (count >= selection_count && selection_count >= 0)
	{
		if (selection_count > count - selection_count)
		{
			selection_count = count - selection_count;
		}

		result = permutations(count, selection_count);
		for (divisor = selection_count; divisor > 1; divisor--)
		{
			result /= divisor;
		}
	}

	return result;
}

boolean permute(
	short base,
	short count,
	short *indices)
{
	short index;

	match_assert("c:\\halo\\SOURCE\\math\\probability.c", 77, base>0);
	match_assert("c:\\halo\\SOURCE\\math\\probability.c", 78, count>0);
	match_assert("c:\\halo\\SOURCE\\math\\probability.c", 79, indices);

	for (index = 0; index < count; index++)
	{
		if (indices[index] < 0 || indices[index] >= base)
		{
			for (index = 0; index < count; index++)
			{
				indices[index] = 0;
			}

			return TRUE;
		}
	}

	for (index = count - 1; index >= 0; index--)
	{
		if (indices[index] < base - 1)
		{
			indices[index]++;
			index++;

			for (; index < count; index++)
			{
				indices[index] = 0;
			}

			return TRUE;
		}
	}

	return FALSE;
}

boolean combine(
	short base,
	short count,
	short *indices)
{
	short index;

	match_assert("c:\\halo\\SOURCE\\math\\probability.c", 119, base>=count);
	match_assert("c:\\halo\\SOURCE\\math\\probability.c", 120, count>0);
	match_assert("c:\\halo\\SOURCE\\math\\probability.c", 121, indices);

	for (index = 0; index < count; index++)
	{
		if (indices[index] < 0 ||
			indices[index] >= base ||
			(index > 0 && indices[index] <= indices[index - 1]))
		{
			for (index = 0; index < count; index++)
			{
				indices[index] = index;
			}

			return TRUE;
		}
	}

	for (index = count - 1; index >= 0; index--)
	{
		if (indices[index] < base - count + index)
		{
			indices[index]++;
			index++;

			for (; index < count; index++)
			{
				indices[index] = indices[index - 1] + 1;
			}

			return TRUE;
		}
	}

	return FALSE;
}

/* ---------- private code */