source file of the LilyPond music typesetter
- (c) 1997--2006 Jan Nieuwenhuizen <janneke@gnu.org>
+ (c) 1997--2007 Jan Nieuwenhuizen <janneke@gnu.org>
Han-Wen Nienhuys <hanwen@xs4all.nl>
*/
factor_ = Rational (1, 1);
}
+Duration::Duration (Rational r, bool scale)
+{
+ factor_ = Rational (1, 1);
+
+ if (r.num () == 0.0)
+ {
+ durlog_ = 0;
+ dots_ = 0;
+ }
+ else
+ {
+ /* we want to find the integer k for which 2q/p > 2^k >= q/p.
+ It's simple to check that k' = \floor \log q - \floor \log p
+ satisfies the left inequality and is within a factor of 2 of
+ satistying the right one. Therefore either k = k' or k = k'+1 */
+
+ int p = r.num ();
+ int q = r.den ();
+ int k = intlog2 (q) - intlog2 (p);
+ if ((p << k) < q)
+ k++;
+
+ assert ((p << k) >= q && (p << (k-1)) < q);
+
+ /* If we were to write out log (p/q) in base 2, then the position of the
+ first non-zero bit (ie. k in our notation) would be the durlog
+ and the number of consecutive 1s after that bit would be the number of
+ dots */
+ p = (p << k) - q;
+ dots_ = 0;
+ while ((p *= 2) >= q)
+ {
+ p -= q;
+ dots_++;
+ }
+
+ /* we only go up to 64th notes */
+ if (k > 6)
+ {
+ durlog_ = 6;
+ dots_ = 0;
+ }
+ else
+ durlog_ = k;
+
+ if (scale || k > 6)
+ factor_ = r / get_length ();
+ }
+}
+
Duration
Duration::compressed (Rational m) const
{