#!/usr/bin/perl

use strict;
use warnings;

my $TRIANGLE =
'..Z2.X6.V343.T2132312.RI.P4E4.N8A8.L3636363.J313231323132313.Hc..';

DrawPattern1($TRIANGLE);
DrawPattern2($TRIANGLE);
DrawPattern3($TRIANGLE);

#####################################################################
# This function converts the input pattern from plain text to binary.
# Also returns the length of the pattern and a couple of zeros.
# Usage: ($PATTERN, $LENGTH, 0, 0) = GetPattern($TEXT)
#
sub GetPattern
{
  my $PATTERN = defined $_[0] ? $_[0] : '';

  # Remove everything except letters and numbers and periods.
  $PATTERN =~ tr|.0-9A-Za-z||cd;

  # Replace all numbers and letters with characters 00 - 3E
  $PATTERN =~ tr|.0-9A-Za-z|\x40\x00-\x3E|;

  return ($PATTERN, length($PATTERN), 0, 0);
}

#####################################################################
# This function prints a pattern to stdout.
# The pattern should be plain text. Each even numbered letter
# specifies the number of spaces to print, and odd numbered
# letters specify the number of '#' signs to print.
# A period creates a line break.
# Usage: DrawPattern1(STRING)
#
sub DrawPattern1
{
  my ($PATTERN, $LENGTH, $MODE, $c) = GetPattern($_[0]);

  for (my $i = 0; $i < $LENGTH; $i++)
  {
    $c = ord(substr($PATTERN, $i, 1));
    PrintPattern($MODE, $c);
  }
}

#####################################################################
# Prints a number of spaces or pound signs to stdout, or a new line.
# Changes the value of the first argument.
# Usage: PrintPattern(WHAT_TO_PRINT, COUNT)
#
sub PrintPattern
{
  @_ == 2 or return;
  my ($MODE, $COUNT) = @_;
  $COUNT < 64 or return $_[0] = print "\n";
  $_[0] = $MODE = $MODE & 1 ? 32 : 35;
  print chr($MODE) x $COUNT;
}

#####################################################################
# This function does exactly the same thing as DrawPattern1()
# Usage: DrawPattern2(STRING)
#
sub DrawPattern2
{
  my ($PATTERN, $LENGTH, $MODE, $c) = GetPattern($_[0]);

  for (my $i = 0; $i < $LENGTH; $i++)
  {
    $c = ord(substr($PATTERN, $i, 1));
    if ($c == 64) { $MODE = print "\n"; next; }
    print chr($MODE = $MODE & 1 ? 32 : 35) x $c;
  }
}

#####################################################################
# This function does exactly the same thing as DrawPattern1()
# Usage: DrawPattern3(STRING)
#
sub DrawPattern3
{
  my ($PATTERN, $LENGTH, $MODE, $c) = GetPattern($_[0]);

  # This is nice but won't work:
  my $code_ref = \"if (\$c == 64) { \$MODE = print \"\\n\"; next; }"
      . " print chr(\$MODE = \$MODE & 1 ? 32 : 35) x \$c; ";

  # This will work:
  my $CODE_REF = \"if (\$c == 64) { \$MODE = print \"\\n\"; }" .
    " else { print chr(\$MODE = \$MODE & 1 ? 32 : 35) x \$c; } ";


  for (my $i = 0; $i < $LENGTH; $i++)
  {
    $c = ord(substr($PATTERN, $i, 1));
    eval($$CODE_REF);

    # This is, of course, not a very good idea, because
    # repeatedly using eval() slows down the program.

  }
}

#####################################################################