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/* $Id */

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/**

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 * @file

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 * Implements a Fixed-point data type.

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 * This files defines a new data type

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 * "FixedT<Tstorage, Tdec_bits>", which can be used to compute fractional

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 * numbers without having to worry about network stability (because

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 * there is no real rounding taking place.

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 * Use "Fixed" for the defaults values (48 bits integral part, 16 bits

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 * fractional part) or "FixedT<typename, int>" for flexible sizes. "int"

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 * number of bits are taken from a variable of "typename" for the fractional

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 * representation, the rest stays available for the integral part.

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 * @warning More than 16 bits fractional should not be used when working

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 * with large integers.

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 * @warning More than 31 fractional bits are not supported, and will

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 * trigger a compiler warning with appropriate settings.

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 * @warning There are no warnings for buffer overflows. Those are very likely

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 * to happen with divisions, as those first shift the numerator by the number

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 * of fractional bits. Use multiplication with the reciprocal whereever

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 * it is possible.

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 * @warning Please use signed variables for storage at the moment ONLY

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 *

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 * Variables can be initialized:

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 * 	- with integers: "FixedT<int, 9> a = -5"

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 * 	- with fractionals: "FixedT<int64, 11> b(7, 2);" where the first number is

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 * the numerator and the second is the denominator.

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 * 	- not at all: "Fixed c;", which will automatically set c to zero.

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 *

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 * @example fixed_ex.cpp How to initialize Fixed-point data types

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 */

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/* Included to overload the stream operator << */

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#include <iostream>

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/* Needed for some ottd-specific data types */

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#include "stdafx.h"

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/**

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 * Base Class for storing fixed-point data types.

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 * Fixed-point data types are stored in a single integer-type variable

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 * (Tstorage) of which a certain number of bits (Tdec_bits) is used to

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 * represent the fractional part of the number.

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 */

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template <typename Tstorage, int Tdec_bits>

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class FixedRawT {

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public:

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	/** The number of bits that represent the fractional */

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	static const int dec_bits = Tdec_bits;

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	/** The storage of the number itself */

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	Tstorage m_data;

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	/**

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	 * Basic constructor for integer arguments.

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	 * @param value The raw value to which we want to initialize

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	 */

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	template <typename T>

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	FixedRawT(T value) : m_data(value) {}

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	/**

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	 * Make sure that a Fixed variable is always inizialized to zero by default.

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	 * We need this ctor so that we can declare variable without

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	 * the need to initialize it explicitly

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	 */

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	FixedRawT() : m_data (0) {}

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	/**

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	 * Returns the biggest integral number we can represent

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	 */

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	int64 FIXED_MAX() const { return m_maximum; }

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	/**

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	 * Returns the biggest integral number we can represent

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	 */

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	int64 FIXED_MIN() const { return m_minimum; }

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private:

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	/** The largest number we can hold */

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	static const int64 m_maximum = +(1ULL << ((sizeof(Tstorage) * 8) - Tdec_bits - 1)) - 1;

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	/** The smallest number we can hold */

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	static const int64 m_minimum = -(1ULL << ((sizeof(Tstorage) * 8) - Tdec_bits - 1)) - 0;

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};

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/* forward-declare some structs */

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template <typename Tstorage, int Tdec_bits> class FixedT;

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template <typename T> struct FixedHelperT;

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/**

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 * Specialization of FixedHelperT. Used to decimal-align two variables of Fixed type.

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 */

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template <typename Tstorage, int Tdec_bits> struct FixedHelperT<FixedRawT<Tstorage, Tdec_bits> >

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{

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	/** The number of bits used for the fraction */

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	static const int dec_bits = Tdec_bits;

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	/**

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	 * Gives the raw data of a FixedRaw

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	 * @param t The number to return

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	 */

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	static int64 Raw(const FixedRawT<Tstorage, Tdec_bits>& t) {return (int64)t.m_data;}

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	/**

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	 * Returns the data from FixedRawT aligned so that it is aligned to a given number

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	 * @param t    The number to be aligned

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	 * @param bits The number of bits in the fractional part to be aligned to

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	 */

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	static int64 Raw(const FixedRawT<Tstorage, Tdec_bits>& t, int bits)

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	{

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		return (((int64)t.m_data) << (bits > Tdec_bits ? bits - Tdec_bits : 0)) >> (bits < Tdec_bits ? Tdec_bits - bits : 0);

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	}

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};

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/**

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 * Specialization of FixedHelperT. Used to decimal-align two variables of Fixed type.

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 */

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template <typename Tstorage, int Tdec_bits> struct FixedHelperT<FixedT<Tstorage, Tdec_bits> > : public FixedHelperT<FixedRawT<Tstorage, Tdec_bits> > {};

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/**

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 * General implementation of FixedHelperT. This tempate makes sure that

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 * some number supplied is properly aligned at the decimal

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 */

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template <typename T> struct FixedHelperT

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{

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	/** This version of FixedHelperT is only used for full integers, so assume the number of dec_bits to be zero */

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	static const int dec_bits = 0;

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	/** Converts a full integer to one that has a given number of fractional bits, assumes

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	 * the number of fractional bits to be zero.

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	 * @param t the number to be converted

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	 */

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	static int64 Raw(const T& t) {return (int64)t;}

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	/**

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	 * Converts a full integer to one that has a given number of fractional bits

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	 * @param bits the number of bits for the fraction

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	 * @param t    the number to be converted

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	 */

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	static int64 Raw(const T& t, int bits) {return ((int64)t) << bits;}

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};

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/**

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 * A class that defines a fixed-point data type, which a variable length and precision.

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 * The data type that is defined is a fixed-point variable that has and number of Tdec_bits

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 * bits to represent the fractional part, the remaining bits of Tstorage are then used for

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 * the integer part of the number. This means, we always need to make a trade-off between

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 * the precision we want (higher number in Tdec_bits) and the range (smaller number of

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 * Tdec_bits). This class here only defines the constructors and the operators, everything

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 * else is happning in helper classes.

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 * @note for usage of fprintf and similar, explicit casts are needed (double or int64).

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 */

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template <typename Tstorage, int Tdec_bits> class FixedT : public FixedRawT<Tstorage, Tdec_bits> {

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/* private block up here, because we need the typedef later on */

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private:

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	/** We shortcut the underlying data type to "Raw", to save typing */

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	typedef FixedRawT<Tstorage, Tdec_bits> Raw;

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public:

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	/**

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	 * Ctor for assignment with other, non floating, variable types

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	 * @param value The Value we should assign to the Fixed

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	 */

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	template <typename T> FixedT(T value) : Raw(FixedHelperT<T>::Raw(value, Tdec_bits)) {}

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	/** As a constructor without initializing, just use the one that Raw uses. Sets a variable to zero */

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	FixedT() : Raw() {}

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	/**

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	 * Ctor for use with a fraction, useful for initing a variable to a non-integer number at declaration.

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	 * @param numerator   The Nominator of the fraction

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	 * @param denominator The Denominator of the fraction

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	 */

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	FixedT(int numerator, int denominator) {Raw::m_data = ((int64)numerator << Raw::dec_bits) / (int64)denominator;}

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	/**

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	 * Cast to a double (for outputs)

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	 */

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	operator double() const

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	{

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		return (double)Raw::m_data / (1 << Raw::dec_bits);

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	}

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	/**

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	 * Equality operator

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	 * @param comparator The non-floating point variable we want to compare against

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	 */

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	template <typename T>

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	bool operator ==(const T &comparator) const { return Raw::m_data == (Tstorage)FixedHelperT<T>::Raw(comparator, Tdec_bits); }

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	/**

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	 * Inequality operator

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	 * @param comparator The non-floating point variable we want to compare against

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	 */

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	template <typename T>

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	bool operator !=(const T &comparator) const { return Raw::m_data != (Tstorage)FixedHelperT<T>::Raw(comparator, Tdec_bits); }

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	/**

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	 * Greater or equal operator

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	 * @param comparator The non-floating point variable we want to compare against

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	 */

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	template <typename T>

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	bool operator >=(const T &comparator) const { return Raw::m_data >= (Tstorage)FixedHelperT<T>::Raw(comparator, Tdec_bits); }

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	/**

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	 * Less or equal operator

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	 * @param comparator The non-floating point variable we want to compare against

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	 */

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	template <typename T>

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	bool operator <=(const T &comparator) const { return Raw::m_data <= (Tstorage)FixedHelperT<T>::Raw(comparator, Tdec_bits); }

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	/**

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	 * Greater than operator

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	 * @param comparator The non-floating point variable we want to compare against

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	 */

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	template <typename T>

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	bool operator >(const T &comparator) const { return Raw::m_data > (Tstorage)FixedHelperT<T>::Raw(comparator, Tdec_bits); }

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	/**

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	 * Less than operator

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	 * @param comparator The non-floating point variable we want to compare against

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	 */

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	template <typename T>

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	bool operator <(const T &comparator) const { return Raw::m_data < (Tstorage)FixedHelperT<T>::Raw(comparator, Tdec_bits); }

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	/**

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	 * Addition for Fixed-point data types

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	 * @param value The non-floating point number to add

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	 */

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	template <typename T> FixedT operator +(const T &value) const

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	{

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		return Raw(Raw::m_data + (Tstorage)FixedHelperT<T>::Raw(value, Tdec_bits));

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	}

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	/**

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	 * Subtraction for Fixed-point data types

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	 * @param value The non-floating point number to subtract

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	 */

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	template <typename T> FixedT operator -(const T &value) const

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	{

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		return Raw(Raw::m_data - (Tstorage)FixedHelperT<T>::Raw(value, Tdec_bits));

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	}

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	/**

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	 * A simple multiplication for non-floating data types

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	 * @param value The non floating-point factor

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	 */

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	template <typename T> FixedT operator *(const T &value) const

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	{

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		return Raw( (((int64)Raw::m_data) * FixedHelperT<T>::Raw(value)) >> FixedHelperT<T>::dec_bits);

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	}

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	/**

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	 * A simple division for non-floating data types

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	 * @param value The non floating-point divisor

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	 */

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	template <typename T> FixedT operator /(const T &value) const

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	{

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		return Raw( (((int64)Raw::m_data) << FixedHelperT<T>::dec_bits) / FixedHelperT<T>::Raw(value));

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	}

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	/**

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	 * Addition-assignment for Fixed-point data types

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	 * @param value The non-floating point number to add

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	 */

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	template <typename T> FixedT& operator +=(const T &value)

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	{

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		Raw::m_data = Raw::m_data + (Tstorage)FixedHelperT<T>::Raw(value, Tdec_bits);

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		return *this;

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	}

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	/**

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	 * Subtract-assignment for Fixed-point data types

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	 * @param value The non-floating point number to subtract

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	 */

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	template <typename T> FixedT& operator -=(const T &value)

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	{

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		Raw::m_data = Raw::m_data - (Tstorage)FixedHelperT<T>::Raw(value, Tdec_bits);

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		return *this;

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	}

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	/**

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	 * Multiply-assignment for Fixed-point data types

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	 * @param value The non-floating point number to multiply

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	 */

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	template <typename T> FixedT& operator *=(const T &value)

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	{

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		Raw::m_data = ((int64)Raw::m_data * (Tstorage)FixedHelperT<T>::Raw(value)) >> FixedHelperT<T>::dec_bits;

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		return *this;

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	}

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	/**

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	 * Divide-assignment for Fixed-point data types

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	 * @param value The non-floating point number to use as divisor

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	 */

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	template <typename T> FixedT& operator /=(const T &value)

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	{

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		Raw::m_data = (Raw::m_data << FixedHelperT<T>::dec_bits) / (Tstorage)FixedHelperT<T>::Raw(value);

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		return *this;

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	}

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	/**

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	 * Unary minus operator

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	 */

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	FixedT operator -() const { return Raw(-Raw::m_data); }

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	/**

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	 * Stream operator, used for floating point output

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	 * @param os    The stream we are going to write to

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	 * @param value The Fixed-point variable we want to write in the stream

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	 */

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	friend std::ostream& operator << (std::ostream &os, const FixedT &value) { os << (double)value.m_data / (1ULL << Raw::dec_bits); return os; }

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/**

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 * Computes a integral, positive power of a FixedT. Uses an optimized algorithm

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 * to keep computational requirement at bay, by decomposing the power into powers

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 * of two itself.

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 *

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 * @param arg   The number to compute the power for

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 * @param pow   the power

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 * @todo        Add a nice LaTeX forumla to the documentation

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 * @todo        Implement negative powers

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 */

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template <typename Tstorage, int Tdec_bits>

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FixedT<Tstorage, Tdec_bits> pow(const FixedT<Tstorage, Tdec_bits> &arg, int pow)

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{

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	FixedT<int64, Tdec_bits> temp = 1;

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	FixedT<int64, Tdec_bits> mul = arg;

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	if (pow == 0) return (FixedT<Tstorage, Tdec_bits>)1;

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	for (int i = 1; pow > 0; pow >>= 1, i <<= 1, mul *= mul) if (pow & 1) temp *= mul;

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	return temp;

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}

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/**

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 * Computes a single element of the Taylor series for the approximation of the cosine.

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 * A single element of the Taylor series computes as:

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 * \f[

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 *    \frac{(-1)^nx^{2n}}{(2n)!}

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 * \f]

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 * In order to prevent overflows, underflows and other nasty stuff, we do not compute

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 * the numerator and denominator separately in the formula but build a product of

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 * fractions:

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 * \f[

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 *    \frac{x}{2n} * \frac{x}{2n-1} * \frac{x}{2n-2} ...

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 * \f]

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 * @param arg The value of "x" in above formula

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 * @param pow The value of "2n" in above formula

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 * @return    The value of the element of the Taylor series

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 */

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template <typename Tstorage, int Tdec_bits>

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FixedT<Tstorage, Tdec_bits> trigbase(const FixedT<Tstorage, Tdec_bits> &arg, int pow)

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{

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	/* Shortcut for the very first element */

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	if (pow == 0) return (FixedT<Tstorage, Tdec_bits>)1;

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	/* find out the (-1)^n part, element should be negative if n is non-even

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	 * but "pow" already holds 2n, account for that

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	 */

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	bool neg = ( (pow / 2) % 2 > 0);

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	FixedT<Tstorage, Tdec_bits> element = arg / pow;

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	for (--pow; pow > 0; pow --) element *= arg / pow;

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	return (neg) ? -element : element;

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}

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/**

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 * Computes the cosine of an argument using a Taylor series.

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 * @param arg The number to compute the cosine from, assumes arg to be in radians.

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 * @todo      Optimize the two while loops.

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 * @note      It is possible to factor out the series to optimize even further, but is it

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 *            worth the effort? It could reduce the opcount a little.

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 * @see       trigbase, PRECISION

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 */

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template <typename Tstorage, int Tdec_bits>

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FixedT<Tstorage, Tdec_bits> cos(const FixedT<Tstorage, Tdec_bits> &arg)

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{

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	FixedT<Tstorage, Tdec_bits> l_arg = arg;

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	FixedT<Tstorage, Tdec_bits> cosine = 0;

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	/* We've got to adjust the argument around zero, otherwise we will need

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	 * (literally) hundreds of elements

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	 */

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	while (l_arg < -PI) l_arg += PI * 2;

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	while (l_arg >  PI) l_arg -= PI * 2;

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	/* sum up the Taylor elements */

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	for(int i = 0; i < PRECISION; i++) cosine += trigbase(l_arg, 2 * i);

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	return cosine;

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}

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/**

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 * Computes the sine of an argument using a Taylor series, uses the cosine

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 * computation in fact, as \f$sin(x) = cos(x - \frac{\pi}{2}))\f$

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 * @param arg The number to compute the cosine from, assumes arg to be in radians.

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 */

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template <typename Tstorage, int Tdec_bits>

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FixedT<Tstorage, Tdec_bits> sin(const FixedT<Tstorage, Tdec_bits> &arg)

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{

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	return cos(arg - PI / 2);

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}

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