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2114
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1 #!/usr/bin/env perl
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2 # -*- cperl -*-
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3 # Shove interpreter. By Alex Smith.
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4
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5 # Commands:
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6 # ' " Quote a string ('' strings nest inside "" strings and vice versa)
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7 # < v > ^ Change direction of execution
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8 # A V ( ) Pop a string onto the playfield
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9 # space NOP
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10
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11 # ! NOP, but tells the compiler that everything behind the IP will
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12 # never be used (a useful optimisation)
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13 # S NOP, but outputs TOS (without popping) on systems with output
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14 # n NOP, but outputs a newline on systems with output
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15
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16 use strict;
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17
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18 # Read in the program
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19
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20 my $debug = ($#ARGV >= 0 and $ARGV[0] eq '-d' and shift and 1);
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21 my @program = ($#ARGV >= 0 and ($ARGV[0] ne '-f' or (shift and 0)))
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22 ? @ARGV : <>;
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23 chomp for @program;
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24
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25 my $x = 0;
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26 my $y = 0;
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27 my $width = 0; $width = ($width < length $_ ? length $_ : $width) for @program;
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28 my $height = scalar @program;
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29 my $totalrotation = 0;
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30 my @stack = ();
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31 # always going right, we rotate the program if necessary to ensure this
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32
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33 # Pads its argument to width $width.
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34 sub widthpad {
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35 my $s = shift;
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36 return $s . (' ' x ($width - length $s));
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37 }
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38
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39 # Rotates the program clockwise (arg = 1), 180 degrees (arg = 2),
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40 # or anticlockwise (arg = 3)
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41 sub rotateprogram {
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42 my $amount = shift;
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43 $amount or return;
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44 $totalrotation += $amount;
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45 $totalrotation %= 4;
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46 if ($amount >= 2) {
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47 @program = reverse @program;
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48 $_ = reverse widthpad $_ for @program;
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49 $x = $width - 1 - $x;
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50 $y = $height - 1 - $y;
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51 tr/<v>^AV()/>^<vVA)(/ for @program;
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52 $amount == 2 and return;
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53 } else {
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54 $_ = widthpad $_ for @program;
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55 }
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56 my @newprog = ();
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57 # We repeatedly move the leftmost column of @program to the top row
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58 # of @newprog.
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59 while (length $program[0]) {
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60 my $build='';
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61 $build = (substr $_, 0, 1, '') . $build for @program;
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62 push @newprog, $build;
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63 }
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64 @program = @newprog;
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65 tr/<^>v(A)V/^>v<A)V(/ for @program;
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66 ($width, $height) = ($height, $width);
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67 ($x, $y) = ($width - 1 - $y, $x);
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68 }
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69
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70 sub shove {
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71 my $sx = shift;
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72 my $sy = shift;
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73 if($sx < 0) {
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74 $_ = ' '.$_ for @program;
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75 $x++;
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76 $sx++;
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77 $width++;
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78 }
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79 if($sx >= $width) {
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80 $width++;
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81 }
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82 if($sy < 0) {
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83 unshift @program, "";
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84 $y++;
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85 $sy++;
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86 $height++;
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87 }
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88 if($sy >= $height) {
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89 push @program, "";
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90 $height++;
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91 }
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92 scalar @stack or die "Empty stack when shoving.";
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93 $program[$sy] = widthpad $program[$sy];
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94 ($x > $sx && $y == $sy) and $x += length $stack[0];
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95 substr $program[$sy], $sx, 0, shift @stack;
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96 $program[$sy] =~ s/\ +$//;
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97 $width < length $program[$sy] and $width = length $program[$sy];
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98 }
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99
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100 sub showprogram {
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101 my $tr = $totalrotation;
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102 print "\nactual size: ($width, $height), pos: ($x, $y)\n";
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103 rotateprogram ((4-$tr)%4);
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104 $program[$y] = widthpad $program[$y];
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105 my $c = substr $program[$y], $x, 1, '*';
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106 print "rotated for viewing; pos: ($x, $y), dir: $tr\n";
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107 print "stack: ";
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108 print "{$_} " for @stack;
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109 print "\n";
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110 print "$_\n" for @program;
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111 substr $program[$y], $x, 1, $c;
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112 rotateprogram $tr;
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113 scalar <STDIN>;
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114 }
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115
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116 while ($x < $width && $y < $height && $x >= 0 && $y >= 0) {
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117 showprogram if $debug;
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118 my $cmd = substr $program[$y], $x, 1;
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119 # $cmd eq '>' is a nop
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120 $cmd eq '^' and rotateprogram 1;
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121 $cmd eq '<' and rotateprogram 2;
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122 $cmd eq 'v' and rotateprogram 3;
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123 $cmd eq '(' and shove $x-1, $y;
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124 $cmd eq ')' and shove $x+1, $y;
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125 $cmd eq 'A' and shove $x, $y-1;
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126 $cmd eq 'V' and shove $x, $y+1;
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127 $cmd eq 'S' and print $stack[0];
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128 $cmd eq 'n' and print '\n';
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129 if ($cmd eq '!') {
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130 substr $_, 0, $x, '' for @program;
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131 $width -= $x;
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132 $x = 0;
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133 }
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134 if ($cmd eq '"' || $cmd eq "'") {
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135 my $quotecount = 1;
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136 my $lws = $cmd eq "'";
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137 my $newpush = "";
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138 while($quotecount) {
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139 $x++;
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140 $x < $width or die "Unterminated string.";
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141 $cmd = substr $program[$y], $x, 1;
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142 $cmd eq "'" and ($quotecount += ($lws ? -1 : 1)), ($lws = !$lws);
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143 $cmd eq '"' and ($quotecount += ($lws ? 1 : -1)), ($lws = !$lws);
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144 $quotecount and $newpush .= $cmd;
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145 }
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146 unshift @stack, $newpush;
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147 }
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148 $x++; # move to next command
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149 }
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