2 rational.cc -- implement Rational
4 source file of the Flower Library
6 (c) 1997--2007 Han-Wen Nienhuys <hanwen@xs4all.nl>
16 #include "string-convert.hh"
17 #include "libc-extension.hh"
20 Rational::to_double () const
22 if (sign_ == -1 || sign_ == 1 || sign_ == 0)
23 return ((double)sign_) * num_ / den_;
37 operator << (ostream &o, Rational r)
45 Rational::abs () const
47 return Rational (num_, den_);
51 Rational::trunc_rat () const
53 return Rational (num_ - (num_ % den_), den_);
62 Rational::Rational (int n, int d)
64 sign_ = ::sign (n) * ::sign (d);
70 Rational::Rational (int n)
79 Rational::set_infinite (int s)
81 sign_ = ::sign (s) * 2;
85 Rational::operator - () const
93 Rational::div_rat (Rational div) const
97 return r.trunc_rat ();
101 Rational::mod_rat (Rational div) const
104 r = (r / div - r.div_rat (div)) * div;
110 copy & paste from scm_gcd (GUILE).
124 /* Determine a common factor 2^k */
125 while (!(1 & (u | v)))
131 /* Now, any factor 2^n can be eliminated */
157 Rational::normalize ()
176 int g = gcd (num_, den_);
183 Rational::sign () const
185 return ::sign (sign_);
189 Rational::compare (Rational const &r, Rational const &s)
191 if (r.sign_ < s.sign_)
193 else if (r.sign_ > s.sign_)
195 else if (r.is_infinity ())
197 else if (r.sign_ == 0)
199 return r.sign_ * ::sign (int (r.num_ * s.den_) - int (s.num_ * r.den_));
203 compare (Rational const &r, Rational const &s)
205 return Rational::compare (r, s);
209 Rational::operator %= (Rational r)
216 Rational::operator += (Rational r)
220 else if (r.is_infinity ())
224 int lcm = (den_ / gcd (r.den_, den_)) * r.den_;
225 int n = sign_ * num_ * (lcm / den_) + r.sign_ * r.num_ * (lcm / r.den_);
227 sign_ = ::sign (n) * ::sign (d);
236 copied from libg++ 2.8.0
238 Rational::Rational (double x)
246 double mantissa = frexp (x, &expt);
248 const int FACT = 1 << 20;
251 Thanks to Afie for this too simple idea.
253 do not blindly substitute by libg++ code, since that uses
254 arbitrary-size integers. The rationals would overflow too
258 num_ = (unsigned int) (mantissa * FACT);
259 den_ = (unsigned int) FACT;
285 Rational::operator *= (Rational r)
287 sign_ *= ::sign (r.sign_);
288 if (r.is_infinity ())
303 Rational::operator /= (Rational r)
316 Rational::operator -= (Rational r)
323 Rational::to_string () const
327 string s (sign_ > 0 ? "" : "-");
328 return string (s + "infinity");
331 string s = ::to_string (num ());
332 if (den () != 1 && num ())
333 s += "/" + ::to_string (den ());
338 Rational::to_int () const
340 return (int) num () / den ();
350 Rational::is_infinity () const
352 return sign_ == 2 || sign_ == -2;