fixed point implementation c++, problem

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fixed point implementation c++, problem

fixed point implementation c++, problem in calling a static member function

hello all i am doing fixed point implementation in c++ which is done by the following code

#ifndef __fixed_point_header_h__
#define __fixed_point_header_h__

#include <boost/assert.hpp>
#include <boost/static_assert.hpp> 
#include <boost/operators.hpp>
#include <limits>
#endif
namespace fp {
	template<typename FP, unsigned char I, unsigned char F = std::numeric_limits<FP>::digits - I>

	class fixed_point: boost::ordered_field_operators<fp::fixed_point<FP, I, F>  >
	{     
	BOOST_CONCEPT_ASSERT((boost::Integer<FP>)); 

	BOOST_STATIC_ASSERT(I + F == std::numeric_limits<FP>::digits); 
	
	 
template<int P,typename T = void> 
	struct power2
	{
		static const long long value = 2 * power2<P-1,T>::value;
	};

	template <typename P>
	struct power2<0, P>
	{
		static const long long value = 1;
	};
    
	
	fixed_point(FP value,bool): fixed_(value){ } // initializer list
	
    public:
	typedef FP base_type; ///  fixed point base type of this fixed_point class.
	static const unsigned char integer_bit_count = I; ///  integer part bit count.
	static const unsigned char fractional_bit_count = F; /// fractional part bit count.
    
	fixed_point(){ } /// Default constructor.

   
	//Conversion by constructors.

	//Integer to Fixed point

	template<typename T> fixed_point(T value) : fixed_((FP)value << F)
   {
    BOOST_CONCEPT_ASSERT((boost::Integer<T>)); 
    }
	// Converting constructor.
	//!
	//! This constructor takes a numeric value of type bool and converts it to 
	//! this fixed_point type.
	fixed_point(
		/// The value to convert.
		bool value)
		: fixed_((FP)(value * power2<F>::value))
	{ }
	
	fixed_point(float value) :fixed_((FP)(value * power2<F>::value))
    { }
    
	fixed_point(double value) : fixed_((FP)(value * power2<F>::value))
    { }

    fixed_point(long double value) : fixed_((FP)(value * power2<F>::value))
    { }
     
	/// Copy constructor,explicit definition
	fixed_point(
		/// The right hand side.
		fixed_point<FP, I, F> const& rhs)
		: fixed_(rhs.fixed_)
	{ }

	// copy-and-swap idiom.

    /// Copy assignment operator.
	fp::fixed_point<FP, I, F> & operator =(fp::fixed_point<FP, I, F> const& rhs)
	{
	fp::fixed_point<FP, I, F> temp(rhs); 
	swap(temp); .
	return *this;  //return by reference
    }
	/// Exchanges the elements of two fixed_point objects.
	void swap(
		/// The right hand side.
		fp::fixed_point<FP, I, F> & rhs)
	{
		std::swap(fixed_, rhs.fixed_);
	}
      
	bool operator <(
		/// Right hand side.
		fp::fixed_point<FP, I, F> const& rhs) const
	{
		return 
			fixed_ < rhs.fixed_;  //return by value
	}

	bool operator ==(
		/// Right hand side.
		fp::fixed_point<FP, I, F> const& rhs) const
	{
		return 
			fixed_ == rhs.fixed_; //return by value
    }
	/// Negation operator.
	bool operator !() const
	{
		return fixed_ == 0; //return true if equal to zero, false otherwise.
	}	
	/// Unary minus operator.
	
	
	fp::fixed_point<FP, I, F> operator -() const
	{
		fp::fixed_point<FP, I, F> result;
		result.fixed_ = -fixed_;
		return result;     // return The negative value.
	}

	/// Addition.
	
	fp::fixed_point<FP, I, F> & operator +=(fp::fixed_point<FP, I, F> const& summation)
	{
		fixed_ += summation.fixed_;
		return *this; //! /return A reference to this object.
	}

	/// Subtraction.
	
	fp::fixed_point<FP, I, F> & operator -=(fp::fixed_point<FP, I, F> const& subtraction)
	{
		fixed_ -= subtraction.fixed_;
		return *this;  // return A reference to this object.
	}
	

   /// Multiplication.
	
		
	fp::fixed_point<FP, I, F> & operator *=(
		/// Factor for mutliplication.
		fp::fixed_point<FP, I, F> const& factor)
	{
		
	fixed_ = ( fixed_ * (factor.fixed_ >> F) ) +
		( ( fixed_ * (factor.fixed_ & (power2<F>::value-1) ) ) >> F );

		return *this;   //return A reference to this object.
	}

	/// Division.
	
	
	fp::fixed_point<FP, I, F> & operator /=(
		/// Divisor for division.
		fp::fixed_point<FP, I, F> const& divisor)
	{
        
	fp::fixed_point<FP, I, F> fp_z=1;
        
	fp_z.fixed_ = ( (fp_z.fixed_) << (F-2) ) / ( divisor.fixed_ >> (2) );
	*this *= fp_z;

	return *this;   //return A reference to this object

	}
    friend fp::fixed_point<FP, I, F> fmod(fp::fixed_point<FP, I, F> a,fp::fixed_point<FP, I, F> b)
	{
		fp::fixed_point<FP, I, F> result;
		
		result.fixed_ = a.fixed_ % b.fixed_ ;
		return result;
	}
	 
	//cos_sin cordic function
	static fp::fixed_point<FP, I, F> cossin_cordic(fp::fixed_point<int, 15> beta, int n)
    //beta angle in radians
    //n number of iterations
  {
     # define ANGLES_LENGTH 60 //local parameter
     # define KPROD_LENGTH 33  //local parameter

	//Initialization of tables of constants used by CORDIC
    //need a table of arctangents of negative powers of two, in radians: atan(2.^-(0:59));

    fp::fixed_point<FP, I, F> angle;
    fp::fixed_point<FP, I, F> angles[ANGLES_LENGTH] = {
    7.8539816339744830962E-01, // arctan(2.^(0))
    4.6364760900080611621E-01, // arctan(2.^(-1))
    2.4497866312686415417E-01, 
    1.2435499454676143503E-01, 
    6.2418809995957348474E-02, 
    3.1239833430268276254E-02, 
    1.5623728620476830803E-02, 
    7.8123410601011112965E-03, 
    3.9062301319669718276E-03,}; 
	
	//A table of products of reciprocal lengths of vectors [1, 2^-2i]: 1 / sqrt ( 1 + (1/2)^(2i) ).
	fp::fixed_point<FP, I, F> kprod[KPROD_LENGTH] = {    
    0.70710678118654752440, 
    0.63245553203367586640, 
    0.61357199107789634961, 
    0.60883391251775242102, 
    0.60764825625616820093, 
    0.60735177014129595905, 
    0.60727764409352599905, 
    0.60725911229889273006, 
    0.60725447933256232972, 
    0.60725332108987516334, 
    0.60725303152913433540, 
    0.60725295913894481363, 
     };
	double pi = 3.141592653589793;
	int j;
	double sign_factor;
	fp::fixed_point<FP, I, F> factor;
    fp::fixed_point<FP, I, F> poweroftwo;
	fp::fixed_point<FP, I, F> sigma; 
	fp::fixed_point<FP, I, F> c2;
    fp::fixed_point<FP, I, F> s2;
   // fp::fixed_point<FP, I, F> theta;
	
	//  Shift angle to interval [-pi/2,pi/2] and account for signs.
	 if ( beta < - 0.5 * pi )
	 {
     beta = beta + pi;
     sign_factor = -1.0;
     }
     else if ( 0.5 * pi < beta)
     {
     beta = beta - pi;
     sign_factor = -1.0;
     }
     else
     {
     sign_factor = +1.0;
     }
	
	 //  Initialize loop variables: start with 2-vector, cosine of 1 and sine of zero
	 fp::fixed_point<FP, I, F> c= 1.0;   //c will give the value cos(beta)
	 fp::fixed_point<FP, I, F> s= 0.0;  //s will give the value sin(beta)
	
	 poweroftwo = 1;
	 angle =angles[0];
	
	//  Iterations
	for ( j = 1; j <= n; j++ )
    {
    if ( beta < 0.0 )     
      {
      sigma = -1.0;     //theta is -ve sigma is -ve
      }
    else
      {
      sigma = 1.0;    //theta is +ve sigma is +ve
      }
	 
	 factor = sigma * poweroftwo; //used in matrix multiplication
	 
	 //2-by-2 matrix multiplication
	 c2 = c - factor * s;  
	 s2 = factor * c + s;
	 
	 c = c2;
     s = s2; 
	
	 beta = beta - sigma * angle; // update the remaining angle
	 poweroftwo = poweroftwo / 2;
		
	//  Update the angle from table, or eventually by just dividing by two.

    if ( ANGLES_LENGTH < j + 1 )
    {
      angle = angle / 2.0;
    }
    else
    {
      angle = angles[j];
    }
  }
  
   //   Adjust length of output vector to be [cos(beta), sin(beta)]
  
   //  KPROD is essentially constant after a certain point, so if n is
   //  large, just take the last available value.
  
	c = c * kprod [ std::min ( n, KPROD_LENGTH )  ];
	s = s * kprod [ std::min ( n, KPROD_LENGTH )  ];
    
  
   return c;
   return s;
  # undef ANGLES_LENGTH
  # undef KPROD_LENGTH
}
	
	
private:
	/// The value in fixed point format.
	FP fixed_;
 };

} // namespace fmpl

#endif

#endif // __fixed_point_h__

the problem is when i call the cossin_cordic static member function from the test file given below

#include <stdio.h>
#include <cmath>
#include "fixed_point_header.h"
int main()
{
{
     fp::fixed_point<int, 15> fp1 = -3.141592654; // -180°
      for ( int n = 0; n <= 25; n = n + 5 )
       {
   float cos_sin=fp::fixed_point<int, 15>::cossin_cordic(fp1,n);
   printf( "the values are %f\n", float (cos_sin));
  	  }
  	  } 
}

i am getting the error ambiguous overload for âoperator<â in âbeta < ((-5.0e-1) * pi)â
i know the problem the static member function cannot access the members and objects of structs. am i right?

and how to solve this problem, do i need to implement the cossin_cordic function as a non member function.
could someone please help me hw to proceed?

Last edited on

pogrady (677)

I believe that it means that the compiler cannot differentiate between this operator or function and another.

Peter87 (11234)

The error says line 227 is ambiguous.
if ( beta < - 0.5 * pi )

Doesn't it say what the candidates are?

AdrianH (82)

Considering that this won't compile due to quite a few things before the error you are talking about, I cannot comment.

Post code that is at least syntactically correct and then we'll talk. Maybe you pasted your header file incorrectly.

Looks similar to another fixed point lib I saw just recently.

http://www.codeproject.com/Articles/37636/Fixed-Point-Class

Rahul kumar S (69)

@pogrady the compiler cannot access the overloaded operators < , + , - etc,.in the struct as i mentioned the function cossin_cordic as a static member function.

Should i declare as a non static member function or how should i proceed? can you please help me?

Last edited on

Rahul kumar S (69)

i tried cossin_cordic as a non static member function, but as a member function i am getting the
error cossin_cordic was not declared in this scope in Test file.

Last edited on

Rahul kumar S (69)

@peter87 it is saying

candidates are:
operator<(const float, double) <built-in>
operator<(const double, double) <built-in>
operator<(const long double, double) <built-in>
operator<(long long int, double) <built-in>

Rahul kumar S (69)

@coder777do i need to use cossin_cordic as a free function rather than using it as member function. if yes, how do i proceed? can some one please help, i would be greateful!

Last edited on

Rahul kumar S (69)

I can see one potential problem is i have no operator< that takes fixed_point on the LHS and double on the RHS.

so do i do i need to replace all the double,int parameters with the fixedpoint type in cossin_cordic function

Peter87 (11234)

I'm not sure why you operator< is not one of the candidates.

What is inheriting from boost::ordered_field_operators doing? Maybe that somehow causes problems.

Does it work if you convert the rhs to fixed_point type?
if ( beta < fp::fixed_point<int, 15>(- 0.5 * pi) )

Rahul kumar S (69)

yes i tried the same and it works,
the problem is operator< does not takes fixed_point on the LHS and double on the RHS.

when it is fixed_point objects on both the LHS and RHS, it works fine.

Peter87 (11234)

I don't know what boost::ordered_field_operators does but if it makes the fixed_point implicit convertible to float, double, long double and long long that could be the problem. In that case you should probably overload operator< for these types too.

Last edited on

Rahul kumar S (69)

@Peter87as far as i know the boost field operators implement a few operators directly, the others are generated automatically via the ordered_field_operators
//!
//! The ordered_field_operators template takes and generates (==>) the
//! following operators:
//! += ==> + (addable),
//! -= ==> - (subtractable),
//! *= ==> * (multipliable),
//! /= ==> / (dividable),
//! < ==> > , >=, <= (less_than_comparable),
//! == ==> != (equality_comparable).

Last edited on

Rahul kumar S (69)

when i change all the parameters in the cossin_cordic function to the fixed_point types it is working fine and i am getting the results as i expect.

But in the test file how do i print both the return values ie. c, s from the cossin_cordic function.

the below test file prints the cos of fp1

int main()
{
fp::fixed_point<int, 15> fp1 =3.141592654;
for ( int n = 0; n <= 25; n = n + 5 )
   {
   float cos=fp::fixed_point<int, 15>::cossin_cordic(fp1,n);
   printf( "fixedpoint values of cos are %f\n", float (cos));
    }
}

but i need to print the sin value also returned from the cossin_cordic function, so how should i change the test file. can you please help?

Last edited on

Rahul kumar S (69)

i think i need to seperate the cossin_cordic function as cos_cordic and sin_cordic function and return c in the cos_cordic function and return s in the sin_cordic function. am i right? please correct me if am not

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fixed point implementation c++, problem in calling a static member function