Rational representation

[ipdf/code.git] / src / rational.h

diff --git a/src/rational.h b/src/rational.h
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+++ b/src/rational.h
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+#ifndef _RATIONAL_H
+#define _RATIONAL_H
+
+/**
+ * A really shoddy implementation of Rational numbers
+ */
+
+#include "common.h"
+#include <cmath>
+#include <cassert>
+
+namespace IPDF
+{
+
+/** Greatest Common Divisor - Euclid's algorithm **/
+
+template <class T>
+T gcd(const T & a, const T & b)
+{
+       if (a == 1 || a == 0) return 1;
+       if (b == 0) return a;
+       if (b == a) return a;
+       
+       if (a > b) return gcd(a-b,b);
+       return gcd(a, b-a);
+}
+
+/*
+template <class T>
+T gcd(const T & p, const T & q)
+{
+       Debug("p/q = %
+       T g(1);
+       T big(p);
+       T small(q);
+       if (p < q)
+       {
+               big = q;
+               small = p;
+       }
+       if (small == 0)
+               return g;
+       while ((g = big % small) > 0)
+       {
+               big = small;
+               small = g;
+       }
+       return small;
+}       
+*/
+template <class T = int64_t>
+struct Rational
+{
+       /** Construct from a double.**/
+       Rational(double d = 0) : P(d*1e3), Q(1e3) // Possibly the worst thing ever...
+       {
+               Simplify();
+               //CheckAccuracy(d, "Construct from double");
+       }
+
+       Rational(const T & _P, const T & _Q) : P(_P), Q(_Q)
+       {
+               Simplify();
+       }
+
+       Rational(const Rational & cpy) : P(cpy.P), Q(cpy.Q)
+       {
+               Simplify();
+       }
+
+       void Simplify()
+       {
+               if (Q < 0) 
+               {
+                       P = (P < 0) ? -P : P;
+                       Q = -Q;
+               }
+
+               T g = gcd(llabs(P),llabs(Q));
+               P /= g;
+               Q /= g;
+       }
+
+       bool operator==(const Rational & r)  const
+       {
+               if (P == r.P && Q == r.Q) return true;
+               return ToDouble() == r.ToDouble();
+       }
+
+
+       bool operator<(const Rational & r) const {return (P*r.Q < r.P * Q);}
+       bool operator>(const Rational & r) const {return !(*this < r);}
+       bool operator<=(const Rational & r) const {return *this == r || *this < r;}
+       bool operator>=(const Rational & r) const {return *this == r || *this > r;}
+       bool operator!=(const Rational & r) const {return !(*this == r);}
+
+
+
+       /*
+       Rational operator+(const Rational & r) const 
+       {
+               Rational result = (r.P == 0) ? Rational(P,Q) : Rational(P*r.Q + r.P*Q, Q*r.Q);
+               result.CheckAccuracy(ToDouble() + r.ToDouble(),"+");
+               return result;
+       }
+       Rational operator-(const Rational & r) const 
+       {
+               Rational result = (r.P == 0) ? Rational(P,Q) : Rational(P*r.Q - r.P*Q, Q*r.Q);
+               result.CheckAccuracy(ToDouble() - r.ToDouble(),"-");
+               return result;
+       }
+       */
+       Rational operator*(const Rational & r) const 
+       {
+               Rational result(P * r.P, Q * r.Q);
+               if (!result.CheckAccuracy(ToDouble() * r.ToDouble(),"*"))
+               {
+                       Debug("This is %s (%f) and r is %s (%f)", Str().c_str(), ToDouble(), r.Str().c_str(), r.ToDouble());
+               }
+               return result;
+       }
+       Rational operator/(const Rational & r) const 
+       {
+               Rational result = (r.P == 0) ? Rational(P,Q) : Rational(P*r.Q + r.P*Q, Q*r.Q);
+               if (!result.CheckAccuracy(ToDouble() / r.ToDouble(),"*"))
+               {
+                       Debug("This is %s (%f) and r is %s (%f)", Str().c_str(), ToDouble(), r.Str().c_str(), r.ToDouble());
+               }
+               return result;
+       }       
+
+       Rational operator+(const Rational & r) const {return Rational(ToDouble()+r.ToDouble());}
+       Rational operator-(const Rational & r) const {return Rational(ToDouble()-r.ToDouble());}
+       //Rational operator*(const Rational & r) const {return Rational(ToDouble()*r.ToDouble());}
+       //Rational operator/(const Rational & r) const {return Rational(ToDouble()/r.ToDouble());}
+
+       Rational & operator=(const Rational & r) {P = r.P; Q = r.Q; return *this;}
+       Rational & operator+=(const Rational & r) {this->operator=(*this+r); return *this;}
+       Rational & operator-=(const Rational & r) {this->operator=(*this-r); return *this;}
+       Rational & operator*=(const Rational & r) {this->operator=(*this*r); return *this;}
+       Rational & operator/=(const Rational & r) {this->operator=(*this/r); return *this;}
+
+       double ToDouble() const {return (double)(P) / (double)(Q);}
+       bool CheckAccuracy(double d, const char * msg, double threshold = 1e-6) const
+       {
+               double result = fabs(ToDouble() - d) / d;
+               if (result > threshold)
+               {
+                       Warn("(%s) : Rational %s (%f) is not close enough at representing %f (%f vs %f)", msg, Str().c_str(), ToDouble(), d, result, threshold);
+                       return false;
+               }
+               return true;
+       }
+       std::string Str() const
+       {
+               std::stringstream s;
+               s << (int64_t)P << "/" << (int64_t)Q;
+               return s.str();
+       }
+       
+       T P;
+       T Q;
+};
+
+inline Rational<int64_t> pow(const Rational<int64_t> & a, const Rational<int64_t> & b)
+{
+       //TODO:Implement properly
+       int64_t P = std::pow((double)a.P, b.ToDouble());
+       int64_t Q = std::pow((double)a.Q, b.ToDouble());
+       return Rational<int64_t>(P, Q);
+}
+
+
+}
+
+#endif //_RATIONAL_H
+