package ComputerMusic;

#ComputerMusic.pm - Useful computer music related functions
#Copyright (C) 2001  Jacob T. Joaquin
#
#This program is free software; you can redistribute it and/or
#modify it under the terms of the GNU General Public License
#as published by the Free Software Foundation; either version 2
#of the License, or (at your option) any later version.
#
#This program is distributed in the hope that it will be useful,
#but WITHOUT ANY WARRANTY; without even the implied warranty of
#MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#GNU General Public License for more details.
#
#You should have received a copy of the GNU General Public License
#along with this program; if not, write to the Free Software
#Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.

use strict;

sub harmonic {
  # return a relative harmonic of a frequency
  
  my $frequency   = shift;  # The frequency
  my $relative    = shift;  # Relative Harmonic Ratio of the frequency
  my $destination = shift;  # Destination Harmonic of the returned frequency
  my $bend        = shift;  # Detune amount of the returned frequency

  if (defined($bend)) {
    return $frequency * $destination / $relative * $bend;
  }
  else {
    return $frequency * $destination / $relative;
  }
  
}




sub interpolate {
  my $position = shift;  # location of pointer in interpolation
  my $point0   = shift;  # start point of interpolation
  my $point1   = shift;  # end point of interpolation
  my $scale0   = shift;  # scale bias
  my $scale1   = shift;  # scale bias
  my $result;

  $result = ($position - $point0) / ($point1 - $point0);
  return $result * ($scale1 - $scale0) + $scale0;
}




sub interpolateExp {
  my $position = shift;
  my $point0   = shift;
  my $point1   = shift;
  my $scale0   = shift;
  my $scale1   = shift;
  my $amt      = shift;
  my $result;

  $result = ($position - $point0) / ($point1 - $point0);
  $result = (($result + 1) ** $amt) - 1;
  $result = $result/((2 ** $amt)-1);
  return $result * ($scale1 - $scale0) + $scale0;
}




sub pitchToFreq {
  my $STEP = 1.0594630943593;
  my $octave = shift;
  my $note   = shift;
  my $t;

  if ($octave >= 8) { $t = ($octave - 7) * 440 }
  if ($octave <  8) { $t = 440 / (2 ** (8 - $octave)) }

  if($note > 9){ for(1..$note-9) { $t *= $STEP }
  } elsif ($note < 9) { for(1..9-$note) { $t /= $STEP } }

  return $t;
}




1;