#!/usr/bin/perl
# zeta.pl  c.2011 stan kulikowski ii, stankuli@etherways.com, pensacola, fl 32514


$SERIES_DEPTH = 1000000;
&QUERY_DIRICHLET;


sub QUERY_DIRICHLET
{
  my $POWERS = 1;
  my $PRECISION = 0;

  print "\n Dirichlet's zeta function. \n";

  my $OK = 0;

  until ($OK)
  {
    print " How many powers : ";
    chop($POWERS = <>);
    $POWERS = int $POWERS;

    ($POWERS > 1) ? $OK = 1 : print " value must be greater than 1 \n";
  } # until $OK #

  $OK = 0;
  until ($OK)
  {
    print " To what precision : ";
    chop($PRECISION = <>);

    ($PRECISION < 1 && $PRECISION > 0) ? $OK = 1 : print " value must be between 1 and 0 \n";
  } # until $OK #

  &DIRICHLET ($POWERS,$PRECISION);
  print "\n\n"; 

} # QUERY_DIRICHLET #


sub HARMONIC_SERIES
{
  my ($POWER) = @_;

  my $RESULT = 1;
  my $SERIES = $SERIES_DEPTH;

  while ($SERIES > 1)
  {
    $RESULT += 1/($SERIES-- **$POWER);
  } # while ($SERIES > 1) #
  return $RESULT;
} # HARMONIC_SERIES #


sub DIRICHLET
{
  my ($POWERS,$PRECISION) = @_;
  my $POWER = 2;

  print "\n\n\t Power \t Dirichlet's zeta result  (harmonic series depth = $SERIES_DEPTH)\n\n";

  while ($POWER < $POWERS+1)
  {
    print "\t $POWER \t " . &HARMONIC_SERIES ($POWER) . " \n";
    $POWER += $PRECISION;          # problem here at 5.9?
  } # while ($POWER <= $POWERS) #  
} # DIRICHLET #


# eof zeta.pl