2 rational.cc -- implement Rational
4 source file of the Flower Library
6 (c) 1997--2000 Han-Wen Nienhuys <hanwen@cs.uu.nl>
10 #include "rational.hh"
12 #include "string-convert.hh"
13 #include "libc-extension.hh"
15 Rational::operator double () const
17 return (double)sign_ * num_ / den_;
21 operator << (ostream &o, Rational r)
28 Rational::trunc_rat () const
30 return Rational (num_ - (num_ % den_), den_);
39 Rational::Rational (int n, int d)
41 sign_ = ::sign (n) * ::sign (d);
47 Rational::Rational (int n)
55 int gcd (int a, int b)
67 int lcm (int a, int b)
69 return abs (a*b / gcd (a,b));
73 Rational::set_infinite (int s)
75 sign_ = ::sign (s) * 2;
79 Rational::operator - () const
87 Rational::div_rat (Rational div) const
91 return r.trunc_rat ();
95 Rational::mod_rat (Rational div) const
98 r = (r / div - r.div_rat (div)) * div;
103 Rational::normalise ()
122 int g = gcd (num_ , den_);
129 Rational::sign () const
131 return ::sign (sign_);
135 Rational::compare (Rational const &r, Rational const &s)
137 if (r.sign_ < s.sign_)
139 else if (r.sign_ > s.sign_)
141 else if (r.infty_b ())
143 else if (r.sign_ == 0)
148 TODO: fix this code; (r-s).sign() is too expensive.
150 return r.sign_ * ::sign (r.num_ * s.den_ - s.num_ * r.den_);
152 return (r - s).sign ();
157 compare (Rational const &r, Rational const &s)
159 return Rational::compare (r, s );
163 Rational::operator %= (Rational r)
165 *this = r.mod_rat (r);
170 Rational::operator += (Rational r)
174 else if (r.infty_b ())
180 int n = sign_ * num_ *r.den_ + r.sign_ * den_ * r.num_;
181 int d = den_ * r.den_;
182 sign_ = ::sign (n) * ::sign (d);
192 copied from libg++ 2.8.0
194 Rational::Rational (double x)
202 double mantissa = frexp (x, &expt);
204 const int FACT = 1 << 20;
207 Thanks to Afie for this too simple idea.
209 do not blindly substitute by libg++ code, since that uses
210 arbitrary-size integers. The rationals would overflow too
214 num_ = (unsigned int) (mantissa * FACT);
215 den_ = (unsigned int) FACT;
242 Rational::operator *= (Rational r)
244 sign_ *= ::sign (r.sign_);
260 Rational::operator /= (Rational r)
273 Rational::operator -= (Rational r)
280 be paranoid about overiding libg++ stuff
283 Rational::operator = (Rational const &r)
290 Rational::str () const
294 String s (sign_ > 0 ? "" : "-" );
295 return String (s + "infinity");
297 String s = to_str (num ());
298 if (den () != 1 && num ())
299 s += "/" + to_str (den ());
304 Rational::to_int () const
306 return num () / den ();