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)
22 return ((double)sign_) * num_ / den_;
34 Rational::operator bool () const
41 operator << (ostream &o, Rational r)
49 Rational::trunc_rat () const
51 return Rational (num_ - (num_ % den_), den_);
60 Rational::Rational (int n, int d)
62 sign_ = ::sign (n) * ::sign (d);
68 Rational::Rational (int n)
76 int gcd (int a, int b)
88 Rational::set_infinite (int s)
90 sign_ = ::sign (s) * 2;
94 Rational::operator - () const
102 Rational::div_rat (Rational div) const
106 return r.trunc_rat ();
110 Rational::mod_rat (Rational div) const
113 r = (r / div - r.div_rat (div)) * div;
118 Rational::normalise ()
137 int g = gcd (num_, den_);
144 Rational::sign () const
146 return ::sign (sign_);
150 Rational::compare (Rational const &r, Rational const &s)
152 if (r.sign_ < s.sign_)
154 else if (r.sign_ > s.sign_)
156 else if (r.is_infinity ())
158 else if (r.sign_ == 0)
160 return r.sign_ * ::sign (int (r.num_ * s.den_) - int (s.num_ * r.den_));
164 compare (Rational const &r, Rational const &s)
166 return Rational::compare (r, s);
170 Rational::operator %= (Rational r)
177 Rational::operator += (Rational r)
181 else if (r.is_infinity ())
185 int lcm = (den_ / gcd (r.den_, den_)) * r.den_;
186 int n = sign_ * num_ * (lcm / den_) + r.sign_ * r.num_ * (lcm / r.den_);
188 sign_ = ::sign (n) * ::sign (d);
197 copied from libg++ 2.8.0
199 Rational::Rational (double x)
207 double mantissa = frexp (x, &expt);
209 const int FACT = 1 << 20;
212 Thanks to Afie for this too simple idea.
214 do not blindly substitute by libg++ code, since that uses
215 arbitrary-size integers. The rationals would overflow too
219 num_ = (unsigned int) (mantissa * FACT);
220 den_ = (unsigned int) FACT;
246 Rational::operator *= (Rational r)
248 sign_ *= ::sign (r.sign_);
249 if (r.is_infinity ())
264 Rational::operator /= (Rational r)
277 Rational::operator -= (Rational r)
284 Rational::to_string () const
288 string s (sign_ > 0 ? "" : "-");
289 return string (s + "infinity");
292 string s = ::to_string (num ());
293 if (den () != 1 && num ())
294 s += "/" + ::to_string (den ());
299 Rational::to_int () const
301 return (int) num () / den ();
311 Rational::is_infinity () const
313 return sign_ == 2 || sign_ == -2;