lily/misc.cc

   1 /*
   2   misc.cc -- implement various stuff
   3
   4   source file of the GNU LilyPond music typesetter
   5
   6   (c)  1997--2000 Han-Wen Nienhuys <hanwen@cs.uu.nl>
   7     Jan Nieuwenhuizen <janneke@gnu.org>
   8 */
   9
  10 #include <math.h>
  11 #include "misc.hh"
  12
  13 int
  14 intlog2(int d)
  15 {
  16   int i=0;
  17   while (!(d&1))
  18     {
  19         d/= 2;
  20         i++;
  21     }
  22   assert (!(d/2));
  23   return i;
  24 }
  25
  26 double
  27 log_2(double x)
  28 {
  29   return log (x)  /log (2.0);
  30 }
  31
  32
  33 static int
  34 comp (Real const &a, Real const &b)
  35 {
  36   return sign (a-b);
  37 }
  38
  39 Interval
  40 quantise_iv (Array<Real> positions, Real x)
  41 {
  42   positions.sort (comp);
  43   Real period = positions.top () - positions[0];
  44
  45   int n =  int ((x - positions[0]) / period);
  46   Real frac = (x - positions[0] ) -  n * period;
  47
  48   while (frac < 0)
  49     {
  50       frac += period;
  51       n --;
  52     }
  53
  54   Real px = frac + positions[0];
  55   assert ( positions[0] <= px && px <= positions.top ());
  56   int i=0;
  57   for (; i < positions.size () - 1; i++)
  58     {
  59       if (positions[i] <= px && px <= positions[i+1])
  60         break;
  61     }
  62
  63   return Interval (positions[i] , positions[i+1]) + period * n;
  64 }