2 rational.cc -- implement Rational
4 source file of the Flower Library
6 (c) 1997--1998 Han-Wen Nienhuys <hanwen@stack.nl>
11 #include "string-convert.hh"
12 #include "libc-extension.hh"
14 Rational::operator bool () const
19 Rational::operator int () const
21 return sign_ * num_ / den_;
24 Rational::operator double () const
26 return (double)sign_ * num_ / den_;
30 operator << (ostream &o, Rational r)
39 Rational::truncated () const
41 return Rational(num_ - (num_ % den_), den_);
50 Rational::Rational (int n, int d)
52 sign_ = ::sign (n) * ::sign (d);
60 int gcd (int a, int b)
72 int lcm (int a, int b)
74 return abs (a*b / gcd (a,b));
78 Rational::set_infinite (int s)
80 sign_ = ::sign (s) * 2;
84 Rational::operator - () const
92 Rational::normalise ()
105 int g = gcd (num_ , den_);
112 Rational::sign () const
114 return ::sign (sign_);
118 Rational::infty_b () const
120 return abs (sign_) > 1;
124 Rational::compare (Rational const &r, Rational const &s)
126 if (r.sign_ < s.sign_)
128 else if (r.sign_ > s.sign_)
130 else if (r.infty_b ())
133 return (r - s).sign ();
137 compare (Rational const &r, Rational const &s)
139 return Rational::compare (r, s );
143 Rational::operator += (Rational r)
147 else if (r.infty_b ())
153 int n = sign_ * num_ *r.den_ + r.sign_ * den_ * r.num_;
154 int d = den_ * r.den_;
155 sign_ = ::sign (n) * ::sign(d);
165 copied from libg++ 2.8.0
167 Rational::Rational(double x)
176 const long shift = 15; // a safe shift per step
177 const double width = 32768.0; // = 2^shift
178 const int maxiter = 20; // ought not be necessary, but just in case,
179 // max 300 bits of precision
181 double mantissa = frexp(x, &expt);
182 long exponent = expt;
185 while (mantissa != 0.0 && k++ < maxiter)
188 mantissa = modf(mantissa, &intpart);
190 num_ += (long)intpart;
195 else if (exponent < 0)
213 Rational::operator *= (Rational r)
215 sign_ *= ::sign (r.sign_);
231 Rational::operator /= (Rational r)
244 Rational::operator -= (Rational r)
251 be paranoid about overiding libg++ stuff
254 Rational::operator = (Rational const &r)
260 Rational::Rational (Rational const &r)
265 Rational::operator String () const
271 Rational::str () const
275 String s (sign_ > 0 ? "" : "-" );
276 return String (s + "infinity");
279 if (den () != 1 && num ())
280 s += "/" + String (den ());