diff --git a/23_Checkers/perl/README.md b/23_Checkers/perl/README.md index e69c8b81..4323cf4a 100644 --- a/23_Checkers/perl/README.md +++ b/23_Checkers/perl/README.md @@ -1,3 +1,9 @@ Original source downloaded [from Vintage Basic](http://www.vintage-basic.net/games.html) Conversion to [Perl](https://www.perl.org/) + +Note: This version has lines and columns numbers to help you with choosing the cell +to move from and to, so you don't have to continually count. It also puts a "." only for +blank cells you can move to, which I think makes for a more pleasing look and makes +it easier to play. If you want the original behavior, start the program with an arg +of "-o" for the original behavior. diff --git a/23_Checkers/perl/checkers.pl b/23_Checkers/perl/checkers.pl new file mode 100755 index 00000000..46b8f2d4 --- /dev/null +++ b/23_Checkers/perl/checkers.pl @@ -0,0 +1,351 @@ +#!/usr/bin/perl + +# Checkers program in Perl +# Started with checkers.annotated.bas +# Translated by Kevin Brannen (kbrannen) + +use strict; +use warnings; + +# globals +# +# The current move: (rating, current x, current y, new x, new y) +# 'rating' represents how good the move is; higher is better. +my @ratings = (-99); # (4); # Start with minimum score +# The board. Pieces are represented by numeric values: +# +# - 0 = empty square +# - -1,-2 = X (-1 for regular piece, -2 for king) +# - 1,2 = O (1 for regular piece, 2 for king) +# +# This program's player ("me") plays X. +my @board; # (7,7) +# chars to print for the board, add 2 to the board value as an index to the char +my @chars = ("X*", "X", ".", "O", "O*"); +my $neg1 = -1; # constant holding -1 +my $winner = ""; +my $upgrade = shift(@ARGV) // ""; +$upgrade = $upgrade eq "-o" ? 0 : 1; + +##### + +print "\n"; +print " " x 32, "CHECKERS\n"; +print " " x 15, "CREATIVE COMPUTING MORRISTOWN, NEW JERSEY\n\n\n"; + + +print "THIS IS THE GAME OF CHECKERS. THE COMPUTER IS X,\n"; +print "AND YOU ARE O. THE COMPUTER WILL MOVE FIRST.\n"; +print "SQUARES ARE REFERRED TO BY A COORDINATE SYSTEM.\n"; +print "(0,0) IS THE LOWER LEFT CORNER\n"; +print "(0,7) IS THE UPPER LEFT CORNER\n"; +print "(7,0) IS THE LOWER RIGHT CORNER\n"; +print "(7,7) IS THE UPPER RIGHT CORNER\n"; +print "THE COMPUTER WILL TYPE '+TO' WHEN YOU HAVE ANOTHER\n"; +print "JUMP. TYPE TWO NEGATIVE NUMBERS IF YOU CANNOT JUMP.\n"; +print "ENTER YOUR MOVE POSITION LIKE '0 0' OR '0,0'.\n\n\n"; + +# Initialize the board. Data is 2 length-wise strips repeated. +my @data = (); +for (1 .. 32) { push(@data, (1,0,1,0,0,0,-1,0, 0,1,0,0,0,-1,0,-1)); } +for my $x (0 .. 7) +{ + for my $y (0 .. 7) + { + $board[$x][$y] = shift(@data); + } +} + +# Start of game loop. First, my turn. +while (1) +{ + + # For each square on the board, search for one of my pieces + # and if it can make the best move so far, store that move in 'r' + for my $x (0 .. 7) + { + for my $y (0 .. 7) + { + # Skip if this is empty or an opponent's piece + next if ($board[$x][$y] > -1); + + # If this is one of my ordinary pieces, analyze possible + # forward moves. + if ($board[$x][$y] == -1) + { + for (my $a = -1 ; $a <= 1 ; $a +=2) + { + $b = $neg1; + find_move($x, $y, $a, $b); + } + } + + # If this is one of my kings, analyze possible forward + # and backward moves. + if ($board[$x][$y] == -2) + { + for (my $a = -1 ; $a <= 1 ; $a += 2) + { + for (my $b = -1 ; $a <= 1 ; $b += 2) { find_move($x, $y, $a, $b); } + } + } + } + } + + + if ($ratings[0] == -99) # Game is lost if no move could be found. + { + $winner = "you"; + last; + } + + # Print the computer's move. (Note: chr$(30) is an ASCII RS + # (record separator) code; probably no longer relevant.) + print "FROM $ratings[1],$ratings[2] TO $ratings[3],$ratings[4] "; + $ratings[0] = -99; + + # Make the computer's move. If the piece finds its way to the + # end of the board, crown it. + LOOP1240: { + if ($ratings[4] == 0) + { + $board[$ratings[3]][$ratings[4]] = -2; + last LOOP1240; + } + $board[$ratings[3]][$ratings[4]] = $board[$ratings[1]][$ratings[2]]; + $board[$ratings[1]][$ratings[2]] = 0; + + # If the piece has jumped 2 squares, it means the computer has + # taken an opponents' piece. + if (abs($ratings[1] - $ratings[3]) == 2) + { + $board [($ratings[1]+$ratings[3])/2] [($ratings[2]+$ratings[4])/2] = 0; # Delete the opponent's piece + + # See if we can jump again. Evaluate all possible moves. + my $x = $ratings[3]; + my $y = $ratings[4]; + for (my $a = -2 ; $a <= 2 ; $a += 4) + { + if ($board[$x][$y] == -1) + { + $b = -2; + eval_move($x, $y, $a, $b); + } + if ($board[$x][$y] == -2) + { + for (my $b = -2 ; $b <= 2 ; $b += 4) { eval_move($x, $y, $a, $b); } + } + } + + # If we've found a move, go back and make that one as well + if ($ratings[0] != -99) + { + print "TO $ratings[3], $ratings[4] "; + $ratings[0] = -99; + next LOOP1240; + } + } + } # LOOP1240 + + # Now, print the board + print "\n\n\n"; + for (my $y = 7 ; $y >= 0 ; $y--) + { + my $line = ""; + $line = "$y|" if ($upgrade); + for my $x (0 .. 7) + { + my $c = $chars[$board[$x][$y] + 2]; + $c = ' ' if ($upgrade && (($y % 2 == 0 && $x % 2 == 1) || ($y % 2 == 1 && $x % 2 == 0))); + $line = tab($line, 5*$x+7, $c); + } + print $line; + print " \n\n"; + } + print " _ _ _ _ _ _ _ _\n" if ($upgrade); + print " 0 1 2 3 4 5 6 7\n" if ($upgrade); + print "\n"; + + # Check if either player is out of pieces. If so, announce the + # winner. + my ($z, $t) = (0, 0); + for my $x (0 .. 7) + { + for my $y (0 .. 7) + { + if ($board[$x][$y] == 1 || $board[$x][$y] == 2) { $z = 1; } + if ($board[$x][$y] == -1 || $board[$x][$y] == -2) { $t = 1; } + } + } + if ($z != 1) { $winner = "comp"; last; } + if ($t != 1) { $winner = "you"; last; } + + # Prompt the player for their move. + ($z, $t) = (0, 0); + my ($x, $y, $e, $h, $a, $b); + do { + ($e,$h) = get_pos("FROM:"); + $x = $e; + $y = $h; + } while ($board[$x][$y] <= 0); + do { + ($a,$b) = get_pos("TO:"); + $x = $a; + $y = $b; + } while (!($board[$x][$y] == 0 && abs($a-$e) <= 2 && abs($a-$e) == abs($b-$h))); + + LOOP1750: { + # Make the move and stop unless it might be a jump. + $board[$a][$b] = $board[$e][$h]; + $board[$e][$h] = 0; + if (abs($e-$a) != 2) { last LOOP1750; } + + # Remove the piece jumped over + $board[($e+$a)/2][($h+$b)/2] = 0; + + # Prompt for another move; -1 means player can't, so I've won. + # Keep prompting until there's a valid move or the player gives + # up. + my ($a1, $b1); + do { + ($a1,$b1) = get_pos("+TO:"); + if ($a1 < 0) { last LOOP1750; } + } while ($board[$a1][$b1] != 0 || abs($a1-$a) != 2 || abs($b1-$b) != 2); + + # Update the move variables to correspond to the next jump + $e = $a; + $h = $b; + $a = $a1; + $b = $b1; + } + + # If the player has reached the end of the board, crown this piece + if ($b == 7) { $board[$a][$b] = 2; } + + # And play the next turn. +} + +# Endgame: +print "\n", ($winner eq "you" ? "YOU" : "I"), " WIN\n"; +exit(0); + +########################################### + +# make sure we get a 2 value position +sub get_pos +{ + my $prompt = shift; + my ($p1, $p2); + do { + print "$prompt "; + chomp(my $ans = <>); + ($p1,$p2) = split(/[, ]/, $ans); + } while (!defined($p1) || !defined($p2) || $p1 < -1 || $p2 < -1 || $p1 > 7 || $p2 > 7); + return ($p1,$p2); +} + +# deal with basic's tab() for line positioning +# line = line string we're starting with +# pos = position to start writing +# s = string to write +# returns the resultant string, which might not have been changed +sub tab +{ + my ($line, $pos, $str) = @_; + my $len = length($line); + # if curser is past position, do nothing + if ($len <= $pos) { $line .= " " x ($pos - $len) . $str; } + return $line; +} + +# Analyze a move from (x,y) to (x+a, y+b) and schedule it if it's +# the best candidate so far. +sub find_move +{ + my ($x, $y, $a, $b) = @_; + my $u = $x+$a; + my $v = $y+$b; + + # Done if it's off the board + return if ($u < 0 || $u > 7 || $v < 0 || $ v> 7); + + # Consider the destination if it's empty + eval_jump($x, $y, $u, $v) if ($board[$u][$v] == 0); + + # If it's got an opponent's piece, jump it instead + if ($board[$u][$v] > 0) + { + + # Restore u and v, then return if it's off the board + $u += $a; + $v += $b; + return if ($u < 0 || $v < 0 || $u > 7 || $v > 7); + + # Otherwise, consider u,v + eval_jump($x, $y, $u, $v) if ($board[$u][$v] == 0); + } +} + +# Evaluate jumping (x,y) to (u,v). +# +# Computes a score for the proposed move and if it's higher +# than the best-so-far move, uses that instead by storing it +# and its score in @ratings. +sub eval_jump +{ + my ($x, $y, $u, $v) = @_; + + # q is the score; it starts at 0 + my $q = 0; + + # +2 if it promotes this piece + $q += 2 if ($v == 0 && $board[$x][$y] == -1); + + # +5 if it takes an opponent's piece + $q += 5 if (abs($y-$v) == 2); + + # -2 if the piece is moving away from the top boundary + $q -= 2 if ($y == 7); + + # +1 for putting the piece against a vertical boundary + $q++ if ($u == 0 || $u == 7); + + for (my $c = -1 ; $c <= 1 ; $c += 2) + { + next if ($u+$c < 0 || $u+$c > 7 || $v+$neg1 < 0); + + # +1 for each adjacent friendly piece + if ($board[$u+$c][$v+$neg1] < 0) + { + $q++; + next; + } + + # Prevent out-of-bounds testing + next if ($u-$c < 0 || $u-$c > 7 || $v-$neg1 > 7); + + # -2 for each opponent piece that can now take this piece here + $q -= 2 if ($board[$u+$c][$v+$neg1] > 0 && ($board[$u-$c][$v-$neg1] == 0 || ($u-$c == $x && $v-$neg1 == $y))); + } + + # Use this move if it's better than the previous best + if ($q > $ratings[0]) + { + $ratings[0] = $q; + $ratings[1] = $x; + $ratings[2] = $y; + $ratings[3] = $u; + $ratings[4] = $v; + } +} + +# If (u,v) is in the bounds, evaluate it as a move using +# the sub at 910, so storing eval in @ratings. +sub eval_move +{ + my ($x, $y, $a, $b) = @_; + my $u = $x+$a; + my $v = $y+$b; + return if ($u < 0 || $u > 7 || $v < 0 || $v > 7); + eval_jump($x, $y, $u, $v) if ($board[$u][$v] == 0 && $board[$x+$a/2][$y+$b/2] > 0); +}