2 rational.cc -- implement Rational
4 source file of the Flower Library
6 (c) 1997--2004 Han-Wen Nienhuys <hanwen@cs.uu.nl>
14 #include "string-convert.hh"
15 #include "libc-extension.hh"
17 Rational::operator double () const
19 return (double)sign_ * num_ / den_;
24 operator << (ostream &o, Rational r)
33 Rational::trunc_rat () const
35 return Rational (num_ - (num_ % den_), den_);
44 Rational::Rational (int n, int d)
46 sign_ = ::sign (n) * ::sign (d);
52 Rational::Rational (int n)
60 int gcd (int a, int b)
73 int lcm (int a, int b)
75 return abs (a*b / gcd (a,b));
80 Rational::set_infinite (int s)
82 sign_ = ::sign (s) * 2;
86 Rational::operator - () const
94 Rational::div_rat (Rational div) const
98 return r.trunc_rat ();
102 Rational::mod_rat (Rational div) const
105 r = (r / div - r.div_rat (div)) * div;
110 Rational::normalise ()
129 int g = gcd (num_ , den_);
136 Rational::sign () const
138 return ::sign (sign_);
142 Rational::compare (Rational const &r, Rational const &s)
144 if (r.sign_ < s.sign_)
146 else if (r.sign_ > s.sign_)
148 else if (r.is_infinity ())
150 else if (r.sign_ == 0)
154 return r.sign_ * ::sign (int (r.num_ * s.den_) - int (s.num_ * r.den_));
159 compare (Rational const &r, Rational const &s)
161 return Rational::compare (r, s );
165 Rational::operator %= (Rational r)
167 *this = r.mod_rat (r);
172 Rational::operator += (Rational r)
176 else if (r.is_infinity ())
182 int n = sign_ * num_ *r.den_ + r.sign_ * den_ * r.num_;
183 int d = den_ * r.den_;
184 sign_ = ::sign (n) * ::sign (d);
194 copied from libg++ 2.8.0
196 Rational::Rational (double x)
204 double mantissa = frexp (x, &expt);
206 const int FACT = 1 << 20;
209 Thanks to Afie for this too simple idea.
211 do not blindly substitute by libg++ code, since that uses
212 arbitrary-size integers. The rationals would overflow too
216 num_ = (unsigned int) (mantissa * FACT);
217 den_ = (unsigned int) FACT;
244 Rational::operator *= (Rational r)
246 sign_ *= ::sign (r.sign_);
247 if (r.is_infinity ())
262 Rational::operator /= (Rational r)
275 Rational::operator -= (Rational r)
282 Rational::to_string () const
286 String s (sign_ > 0 ? "" : "-" );
287 return String (s + "infinity");
290 String s = ::to_string (num ());
291 if (den () != 1 && num ())
292 s += "/" + ::to_string (den ());
297 Rational::to_int () const
299 return num () / den ();
309 Rational::is_infinity () const
311 return sign_ == 2 || sign_ == -2;