2 rational.cc -- implement Rational
4 source file of the Flower Library
6 (c) 1997--2006 Han-Wen Nienhuys <hanwen@xs4all.nl>
16 #include "string-convert.hh"
17 #include "libc-extension.hh"
19 Rational::operator double () const
21 if (sign_ == -1 || sign_ == 1 || sign_ == 0)
22 return ((double)sign_) * num_ / den_;
36 operator << (ostream &o, Rational r)
44 Rational::abs () const
46 return Rational (num_, den_);
50 Rational::trunc_rat () const
52 return Rational (num_ - (num_ % den_), den_);
61 Rational::Rational (int n, int d)
63 sign_ = ::sign (n) * ::sign (d);
70 int gcd (int a, int b)
82 Rational::set_infinite (int s)
84 sign_ = ::sign (s) * 2;
88 Rational::operator - () const
96 Rational::div_rat (Rational div) const
100 return r.trunc_rat ();
104 Rational::mod_rat (Rational div) const
107 r = (r / div - r.div_rat (div)) * div;
112 Rational::normalize ()
131 int g = gcd (num_, den_);
138 Rational::sign () const
140 return ::sign (sign_);
144 Rational::compare (Rational const &r, Rational const &s)
146 if (r.sign_ < s.sign_)
148 else if (r.sign_ > s.sign_)
150 else if (r.is_infinity ())
152 else if (r.sign_ == 0)
154 return r.sign_ * ::sign (int (r.num_ * s.den_) - int (s.num_ * r.den_));
158 compare (Rational const &r, Rational const &s)
160 return Rational::compare (r, s);
164 Rational::operator %= (Rational r)
171 Rational::operator += (Rational r)
175 else if (r.is_infinity ())
179 int lcm = (den_ / gcd (r.den_, den_)) * r.den_;
180 int n = sign_ * num_ * (lcm / den_) + r.sign_ * r.num_ * (lcm / r.den_);
182 sign_ = ::sign (n) * ::sign (d);
191 copied from libg++ 2.8.0
193 Rational::Rational (double x)
201 double mantissa = frexp (x, &expt);
203 const int FACT = 1 << 20;
206 Thanks to Afie for this too simple idea.
208 do not blindly substitute by libg++ code, since that uses
209 arbitrary-size integers. The rationals would overflow too
213 num_ = (unsigned int) (mantissa * FACT);
214 den_ = (unsigned int) FACT;
240 Rational::operator *= (Rational r)
242 sign_ *= ::sign (r.sign_);
243 if (r.is_infinity ())
258 Rational::operator /= (Rational r)
271 Rational::operator -= (Rational r)
278 Rational::to_string () const
282 string s (sign_ > 0 ? "" : "-");
283 return string (s + "infinity");
286 string s = ::to_string (num ());
287 if (den () != 1 && num ())
288 s += "/" + ::to_string (den ());
293 Rational::to_int () const
295 return (int) num () / den ();
305 Rational::is_infinity () const
307 return sign_ == 2 || sign_ == -2;