# This file is part of NIT ( http://www.nitlanguage.org ).
#
# Copyright 2004-2008 Jean Privat <jean@pryen.org>
#
# This file is free software, which comes along with NIT.  This software is
# distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
# without  even  the implied warranty of  MERCHANTABILITY or  FITNESS FOR A
# PARTICULAR PURPOSE.  You can modify it is you want,  provided this header
# is kept unaltered, and a notification of the changes is added.
# You  are  allowed  to  redistribute it and sell it, alone or is a part of
# another product.

# Mathematical operations
module math is ldflags "-lm"

import kernel
import collection

in "C header" `{
	#include <stdlib.h>
	#include <math.h>
	#include <time.h>
`}

in "C" `{
	/* Is rand shortcut? */
	static int nit_rand_seeded;
	/* Current rand seed if seeded */
	static unsigned int nit_rand_seed;

	#define NIT_RAND_MAX 0x7fffffff

	/* This algorithm is mentioned in the ISO C standard, here extended
	for 32 bits.  */
	static int
	nit_rand(void) {
		unsigned int next = nit_rand_seed;
		int result;

		next *= 1103515245;
		next += 12345;
		result = (unsigned int) (next / 65536) % 2048;

		next *= 1103515245;
		next += 12345;
		result <<= 10;
		result ^= (unsigned int) (next / 65536) % 1024;

		next *= 1103515245;
		next += 12345;
		result <<= 10;
		result ^= (unsigned int) (next / 65536) % 1024;

		nit_rand_seed = next;

		return result;
	}
`}

redef class Int
	# Returns a random `Int` in `[0 .. self[`.
	fun rand: Int `{
		if (nit_rand_seeded) return (long)(((double)self)*nit_rand()/(NIT_RAND_MAX+1.0));
		return (long)(((double)self)*rand()/(RAND_MAX+1.0));
	`}

	# Returns the result of a binary AND operation on `self` and `i`
	#
	#     assert 0x10 & 0x01 == 0
	fun &(i: Int): Int is intern `{ return self & i; `}

	# Returns the result of a binary OR operation on `self` and `i`
	#
	#     assert 0x10 | 0x01 == 0x11
	fun |(i: Int): Int is intern `{ return self | i; `}

	# Returns the result of a binary XOR operation on `self` and `i`
	#
	#     assert 0x101 ^ 0x110 == 0x11
	fun ^(i: Int): Int `{ return self ^ i; `}

	# Returns the 1's complement of `self`
	#
	#     assert ~0x2F == -48
	fun ~: Int `{ return ~self; `}

	# Returns the square root of `self`
	#
	#     assert 16.sqrt == 4
	fun sqrt: Int `{ return sqrt(self); `}

	# Returns the greatest common divisor of `self` and `o`
	#
	#     assert 54.gcd(24)   == 6
	#     assert -54.gcd(-24) == 6
	#     assert 54.gcd(-24)  == -6
	#     assert -54.gcd(24)  == -6
	#     assert 12.gcd(6)    == 6
	fun gcd(o: Int): Int
	do
		if self < 0 then return -(-self).gcd(o)
		if o < 0 then return -(self.gcd(-o))
		if self == 0 or o == self then return o
		if o == 0 then return self
		if self & 1 == 0 then
			if o & 1 == 1 then
				return (self >> 1).gcd(o)
			else
				return (self >> 1).gcd(o >> 1) << 1
			end
		end
		if o & 1 == 0 then return self.gcd(o >> 1)
		if self > o then return ((self - o) >> 1).gcd(o)
		return ((o - self) >> 1).gcd(self)
	end

	# Is `self` even ?
	#
	#     assert 12.is_even
	fun is_even: Bool do return self % 2 == 0

	# Is `self` odd ?
	#
	#     assert not 13.is_even
	fun is_odd: Bool do return not is_even

	# Is self a prime number ?
	#
	# assert 3.is_prime
	# assert not 1.is_prime
	# assert not 15.is_prime
	fun is_prime: Bool
	do
		if self == 2 then
			return true
		else if self <= 1 or self.is_even then
			return false
		end
		for i in [3..self.sqrt] do
			if self % i == 0 then return false
		end
		return true
	end

	# Returns the `self` raised to the power of `e`.
	#
	#     assert 2 ** 3 == 8
	fun **(e: Int): Int
	do
		return self.to_f.pow(e.to_f).to_i
	end

	# The factorial of `self` (aka `self!`)
	#
	# Returns `1 * 2 * 3 * ... * self-1 * self`
	#
	#     assert 0.factorial == 1  # by convention for an empty product
	#     assert 1.factorial == 1
	#     assert 4.factorial == 24
	#     assert 9.factorial == 362880
	fun factorial: Int
	do
		assert self >= 0
		var res = 1
		var n = self
		while n > 0 do
			res = res * n
			n -= 1
		end
		return res
	end
end

redef class Byte
	# Returns the result of a binary AND operation on `self` and `i`
	#
	#     assert 0x10u8 & 0x01u8 == 0u8
	fun &(i: Byte): Byte is intern `{ return self & i; `}

	# Returns the result of a binary OR operation on `self` and `i`
	#
	#     assert 0x10u8 | 0x01u8 == 0x11u8
	fun |(i: Byte): Byte `{ return self | i; `}

	# Returns the result of a binary XOR operation on `self` and `i`
	#
	#     assert 0x101u8 ^ 0x110u8 == 0x11u8
	fun ^(i: Byte): Byte `{ return self ^ i; `}

	# Returns the 1's complement of `self`
	#
	#     assert ~0x2Fu8 == 0xD0u8
	fun ~: Byte `{ return ~self; `}
end

redef class Float

	# Returns the non-negative square root of `self`.
	#
	#     assert 9.0.sqrt == 3.0
	#     #assert 3.0.sqrt == 1.732
	#     assert 1.0.sqrt == 1.0
	#     assert 0.0.sqrt == 0.0
	fun sqrt: Float `{ return sqrt(self); `}

	# Computes the cosine of `self` (expressed in radians).
	#
	#     #assert pi.cos == -1.0
	fun cos: Float `{ return cos(self); `}

	# Computes the sine of `self` (expressed in radians).
	#
	#     #assert pi.sin == 0.0
	fun sin: Float `{ return sin(self); `}

	# Computes the cosine of x (expressed in radians).
	#
	#     #assert 0.0.tan == 0.0
	fun tan: Float `{ return tan(self); `}

	# Computes the arc cosine of `self`.
	#
	#     #assert 0.0.acos == pi / 2.0
	fun acos: Float `{ return acos(self); `}

	# Computes the arc sine of `self`.
	#
	#     #assert 1.0.asin == pi / 2.0
	fun asin: Float `{ return asin(self); `}

	# Computes the arc tangent of `self`.
	#
	#     #assert 0.0.tan == 0.0
	fun atan: Float `{ return atan(self); `}

	# Returns the absolute value of `self`.
	#
	#     assert 12.0.abs == 12.0
	#     assert (-34.56).abs == 34.56
	#     assert -34.56.abs == -34.56
	fun abs: Float `{ return fabs(self); `}

	# Returns `self` raised at `e` power.
	#
	#     #assert 2.0.pow(0.0) == 1.0
	#     #assert 2.0.pow(3.0) == 8.0
	#     #assert 0.0.pow(9.0) == 0.0
	fun pow(e: Float): Float `{ return pow(self, e); `}

	# Natural logarithm of `self`.
	#
	#     assert 0.0.log.is_inf == -1
	#     #assert 1.0.log == 0.0
	fun log: Float `{ return log(self); `}

	# Logarithm of `self` to base `base`.
	#
	#     assert 100.0.log_base(10.0) == 2.0
	#     assert 256.0.log_base(2.0) == 8.0
	fun log_base(base: Float): Float do return log/base.log

	# Returns *e* raised to `self`.
	fun exp: Float `{ return exp(self); `}

	#     assert 1.1.ceil == 2.0
	#     assert 1.9.ceil == 2.0
	#     assert 2.0.ceil == 2.0
	#     assert (-1.5).ceil == -1.0
	fun ceil: Float `{ return ceil(self); `}

	#     assert 1.1.floor == 1.0
	#     assert 1.9.floor == 1.0
	#     assert 2.0.floor == 2.0
	#     assert (-1.5).floor == -2.0
	fun floor: Float `{ return floor(self); `}

	# Rounds the value of a float to its nearest integer value
	#
	#     assert 1.67.round == 2.0
	#     assert 1.34.round == 1.0
	#     assert -1.34.round == -1.0
	#     assert -1.67.round == -2.0
	fun round: Float `{ return round(self); `}

	# Returns a random `Float` in `[0.0 .. self[`.
	fun rand: Float `{
		if (nit_rand_seeded) return ((self)*nit_rand())/(NIT_RAND_MAX+1.0);
		return ((self)*rand())/(RAND_MAX+1.0);
	`}

	# Returns the euclidean distance from `b`.
	fun hypot_with(b: Float): Float `{ return hypotf(self, b); `}

	# Returns true is self is not a number.
	#
	# As `nan != nan`, `is_nan` should be used to test if a float is the special *not a number* value.
	#
	# ~~~
	# assert nan != nan # By IEEE 754
	# assert nan.is_nan
	# assert not 10.0.is_nan
	# ~~~
	fun is_nan: Bool `{ return isnan(self); `}

	# Is the float an infinite value
	# this function returns:
	#
	#  * 1 if self is positive infinity
	#  * -1 if self is negative infinity
	#  * 0 otherwise
	#
	# ~~~
	# assert 10.0.is_inf == 0
	# assert inf.is_inf == 1
	# assert (-inf).is_inf == -1
	# ~~~
	fun is_inf: Int do
		if native_is_inf then
			if self < 0.0 then return -1
			return 1
		end
		return 0
	end

	private fun native_is_inf: Bool `{ return isinf(self); `}

	# Linear interpolation between `a` and `b` using `self` as weight
	#
	# ~~~
	# assert  0.0.lerp(0.0, 128.0) == 0.0
	# assert  0.5.lerp(0.0, 128.0) == 64.0
	# assert  1.0.lerp(0.0, 128.0) == 128.0
	# assert -0.5.lerp(0.0, 128.0) == -64.0
	# ~~~
	fun lerp(a, b: Float): Float do return (1.0 - self) * a + self * b

	# Quadratic Bézier interpolation between `a` and `b` with an `handle` using `self` as weight
	#
	# ~~~
	# assert  0.00.qerp(0.0, 32.0, 128.0) == 0.0
	# assert  0.25.qerp(0.0, 32.0, 128.0) == 20.0
	# assert  0.50.qerp(0.0, 32.0, 128.0) == 48.0
	# assert  0.75.qerp(0.0, 32.0, 128.0) == 84.0
	# assert  1.00.qerp(0.0, 32.0, 128.0) == 128.0
	# ~~~
	fun qerp(a, handle, b: Float): Float do
		var p = self
		var i = 1.0 - p
		var r =     i*i * a +
			2.0*i*p * handle +
			    p*p * b
		return r
	end

	# Cubic Bézier interpolation between `a` and `b` with two handles using `self` as weight
	#
	# The Cubic Bézier interpolation is the most common one and use two control points.
	#
	# ~~~
	# assert  0.00.cerp(0.0, 32.0, 128.0, 64.0) == 0.0
	# assert  0.25.cerp(0.0, 32.0, 128.0, 64.0) == 32.5
	# assert  0.50.cerp(0.0, 32.0, 128.0, 64.0) == 68.0
	# assert  0.75.cerp(0.0, 32.0, 128.0, 64.0) == 85.5
	# assert  1.00.cerp(0.0, 32.0, 128.0, 64.0) == 64.0
	# ~~~
	fun cerp(a, a_handle, b_handle, b: Float): Float do
		var p = self
		var i = 1.0 - p
		var r =     i*i*i  * a +
			3.0*i*i*p * a_handle +
			3.0*i*p*p * b_handle +
			    p*p*p * b
		return r
	end
end

# Positive float infinite (IEEE 754)
#
#     assert inf > 10.0
#     assert inf.is_inf == 1
#
# `inf` follows the arithmetic of infinites
#
#     assert (inf - 1.0) == inf
#     assert (inf - inf).is_nan
#
# The negative infinite can be used as `-inf`.
#
#     assert -inf < -10.0
#     assert (-inf).is_inf == -1
fun inf: Float do return 1.0 / 0.0

# Not a Number, representation of an undefined or unrepresentable float (IEEE 754).
#
# `nan` is not comparable with itself, you should use `Float::is_nan` to test it.
#
# ~~~
# assert nan.is_nan
# assert nan != nan # By IEEE 754
# ~~~
#
# `nan` is the quiet result of some undefined operations.
#
# ~~~
# assert (1.0 + nan).is_nan
# assert (0.0 / 0.0).is_nan
# assert (inf - inf).is_nan
# assert (inf / inf).is_nan
# assert (-1.0).sqrt.is_nan
# ~~~
fun nan: Float do return 0.0 / 0.0

redef class Collection[ E ]
	# Return a random element form the collection
	# There must be at least one element in the collection
	#
	# ~~~
	# var x = [1,2,3].rand
	# assert x == 1 or x == 2 or x == 3
	# ~~~
	fun rand: E
	do
		if is_empty then abort
		var rand_index = length.rand

		for e in self do
			if rand_index == 0 then return e
			rand_index -= 1
		end
		abort
	end

	# Return a new array made of elements in a random order.
	#
	# ~~~
	# var a = [1,2,1].to_shuffle
	# assert a == [1,1,2] or a == [1,2,1] or a == [2,1,1]
	# ~~~
	fun to_shuffle: Array[E]
	do
		var res = self.to_a
		res.shuffle
		return res
	end

	# Return a new array made of (at most) `length` elements randomly chosen.
	#
	# ~~~
	# var a = [1,2,1].sample(2)
	# assert a == [1,1] or a == [1,2] or a == [2,1]
	# ~~~
	#
	# If there is not enough elements, then the result only contains them in a random order.
	# See `to_shuffle`.
	#
	# ENSURE `result.length == self.length.min(length)`
	#
	# Note: the default implementation uses the Reservoir Algorithm
	fun sample(length: Int): Array[E]
	do
		if length >= self.length then return to_shuffle

		var res = new Array[E].with_capacity(length)
		var it = iterator
		for i in [0..length[ do
			res[i] = it.item
			it.next
		end
		res.shuffle
		for i in [length+1..self.length] do
			var j = i.rand
			if j < length then
				res[j] = it.item
			end
			it.next
		end
		return res
	end
end

redef class SequenceRead[E]
	# Optimized for large collections using `[]`
	redef fun rand
	do
		assert not is_empty
		return self[length.rand]
	end
end

redef class AbstractArray[E]
	# Reorder randomly the elements in self.
	#
	# ~~~
	# var a = new Array[Int]
	#
	# a.shuffle
	# assert a.is_empty
	#
	# a.add 1
	# a.shuffle
	# assert a == [1]
	#
	# a.add 2
	# a.shuffle
	# assert a == [1,2] or a == [2,1]
	# ~~~
	#
	# ENSURE self.shuffle.has_exactly(old(self))
	fun shuffle
	do
		for i in [0..length[ do
			var j = i + (length-i).rand
			var tmp = self[i]
			self[i] = self[j]
			self[j] = tmp
		end
	end
end

redef class Sys
	init
	do
		srand
	end
end

# Computes the arc tangent given `y` and `x`.
#
#     assert atan2(-0.0, 1.0) == -0.0
#     assert atan2(0.0, 1.0) == 0.0
fun atan2(y: Float, x: Float): Float `{ return atan2(y, x); `}

# Approximate value of **pi**.
fun pi: Float do return 3.14159265

# Initialize the pseudo-random generator with the given seed.
# The pseudo-random generator is used by the method `rand` and other to generate sequence of numbers.
# These sequences are repeatable by calling `srand_from` with a same seed value.
#
# ~~~~
# srand_from(0)
# var a = 10.rand
# var b = 100.rand
# srand_from(0)
# assert 10.rand == a
# assert 100.rand == b
# ~~~~
fun srand_from(x: Int) `{ nit_rand_seeded = 1; nit_rand_seed = (unsigned int)x; `}

# Reinitialize the pseudo-random generator used by the method `rand` and other.
# This method is automatically invoked at the begin of the program, so usually, there is no need to manually invoke it.
# The only exception is in conjunction with `srand_from` to reset the pseudo-random generator.
fun srand `{ nit_rand_seeded = 0; srand((unsigned int)time(NULL)); `}