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 /*
  14   Return the 2-log, rounded down
  15  */
  16 int
  17 intlog2(int d)
  18 {
  19   assert (d);
  20   int i=0;
  21   while ((d != 1))
  22     {
  23       d/= 2;
  24       i++;
  25     }
  26
  27   assert (!(d/2));
  28   return i;
  29 }
  30
  31 double
  32 log_2(double x)
  33 {
  34   return log (x)  /log (2.0);
  35 }
  36
  37
  38 static int
  39 comp (Real const &a, Real const &b)
  40 {
  41   return sign (a-b);
  42 }
  43
  44 Interval
  45 quantise_iv (Array<Real> positions, Real x)
  46 {
  47   positions.sort (comp);
  48   Real period = positions.top () - positions[0];
  49
  50   int n =  int ((x - positions[0]) / period);
  51   Real frac = (x - positions[0] ) -  n * period;
  52
  53   while (frac < 0)
  54     {
  55       frac += period;
  56       n --;
  57     }
  58
  59   Real px = frac + positions[0];
  60   assert ( positions[0] <= px && px <= positions.top ());
  61   int i=0;
  62   for (; i < positions.size () - 1; i++)
  63     {
  64       if (positions[i] <= px && px <= positions[i+1])
  65         break;
  66     }
  67
  68   return Interval (positions[i] , positions[i+1]) + period * n;
  69 }