2 rational.cc -- implement Rational
4 source file of the Flower Library
6 (c) 1997--2006 Han-Wen Nienhuys <hanwen@xs4all.nl>
15 #include "string-convert.hh"
16 #include "libc-extension.hh"
18 Rational::operator double () const
20 return ((double)sign_) * num_ / den_;
23 Rational::operator bool () const
30 operator << (ostream &o, Rational r)
38 Rational::trunc_rat () const
40 return Rational (num_ - (num_ % den_), den_);
49 Rational::Rational (int n, int d)
51 sign_ = ::sign (n) * ::sign (d);
57 Rational::Rational (int n)
65 int gcd (int a, int b)
77 Rational::set_infinite (int s)
79 sign_ = ::sign (s) * 2;
83 Rational::operator - () const
91 Rational::div_rat (Rational div) const
95 return r.trunc_rat ();
99 Rational::mod_rat (Rational div) const
102 r = (r / div - r.div_rat (div)) * div;
107 Rational::normalise ()
126 int g = gcd (num_, den_);
133 Rational::sign () const
135 return ::sign (sign_);
139 Rational::compare (Rational const &r, Rational const &s)
141 if (r.sign_ < s.sign_)
143 else if (r.sign_ > s.sign_)
145 else if (r.is_infinity ())
147 else if (r.sign_ == 0)
149 return r.sign_ * ::sign (int (r.num_ * s.den_) - int (s.num_ * r.den_));
153 compare (Rational const &r, Rational const &s)
155 return Rational::compare (r, s);
159 Rational::operator %= (Rational r)
166 Rational::operator += (Rational r)
170 else if (r.is_infinity ())
174 int lcm = (den_ / gcd (r.den_, den_)) * r.den_;
175 int n = sign_ * num_ * (lcm / den_) + r.sign_ * r.num_ * (lcm / r.den_);
177 sign_ = ::sign (n) * ::sign (d);
186 copied from libg++ 2.8.0
188 Rational::Rational (double x)
196 double mantissa = frexp (x, &expt);
198 const int FACT = 1 << 20;
201 Thanks to Afie for this too simple idea.
203 do not blindly substitute by libg++ code, since that uses
204 arbitrary-size integers. The rationals would overflow too
208 num_ = (unsigned int) (mantissa * FACT);
209 den_ = (unsigned int) FACT;
235 Rational::operator *= (Rational r)
237 sign_ *= ::sign (r.sign_);
238 if (r.is_infinity ())
253 Rational::operator /= (Rational r)
266 Rational::operator -= (Rational r)
273 Rational::to_string () const
277 string s (sign_ > 0 ? "" : "-");
278 return string (s + "infinity");
281 string s = ::to_string (num ());
282 if (den () != 1 && num ())
283 s += "/" + ::to_string (den ());
288 Rational::to_int () const
290 return (int) num () / den ();
300 Rational::is_infinity () const
302 return sign_ == 2 || sign_ == -2;