#!/usr/bin/perl -w
use strict;
use 5.010;

# ------------------------------------------------
# BrainFuck Intepreter -- By: Cody Veal (12/15/08)
# ------------------------------------------------

# OPEN INPUT FILE
die "use the following usage: perl bfi.pl code.txt" if (scalar(@ARGV) != 1);
open my $stream, $ARGV[0] or die "error opening file: $!";

# INITIALIZE POINTER, ARRAY, COUNTER, LOOP STACK
my $top = 5000;

my @array = (1..$top);
my $ptr = 0;
my $i = 0;
my @loops;

for my $i (0..scalar(@array)-1) {
    $array[$i] = 0;
}

# SET UP INPUT
my $input = "";

# concatanates all data into a single line
while (<$stream>) {
    chomp;
    $input .= $_;
}

# substitutes any non-bf characters with nothing (removes all chars that are not bf commands)
$input =~ s/[^\+\-\.\[\],<>]//g;

# ERROR CHECK
my $rbracket = scalar(grep(/[\[]/, $input));
my $lbracket = scalar(grep(/[\]]/, $input));

die "bracket numbers don't match --  ([:$rbracket | ]:$lbracket)" if $rbracket != $lbracket;

# ENTER EXECUTION LOOP
while ($i < length($input)) {
    my $c = substr($input,$i,1);
    $i += 1;
   
    # move pointer to left (wrap to top if ptr is at 0)
    if ($c eq "<") {
        $ptr = $top + 1 if ($ptr == 0);
        $ptr -= 1;
    }
   
    # move pointer to right (wrap to 0 if ptr is at top)
    elsif ($c eq ">") {
        $ptr = -1 if ($ptr == $top);
        $ptr += 1;
    }
   
    # increment value at ptr by 1 (wrap to 0 if value is 255)
    elsif ($c eq "+"){
        $array[$ptr] = -1 if ($array[$ptr] == 255);
        $array[$ptr] += 1;
    }
   
    # decrement value at ptr by 1 (wrap to 255 if value is 0)
    elsif ($c eq "-") {
        $array[$ptr] = 256 if ($array[$ptr] == 0);
        $array[$ptr] -= 1;
    }
   
    # print ascii char of value at ptr
    elsif ($c eq ".") {
        print chr($array[$ptr]);
    }
   
    # get ascii value of char from input and store in value at ptr
    elsif ($c eq ",") {
        my $in = <STDIN>;
        $array[$ptr] = ord(substr($in,0,1));
    }
   
    # store the place after the [ symbol occurs on the top of stack
    elsif ($c eq "[") {
        push @loops, $i;
    }
   
    # if value at ptr is == 0, pop loop location from top of stack, else go to position after last [ was found.
    elsif ($c eq "]") {
        if ($array[$ptr] != 0) {
            $i = $loops[scalar(@loops)-1];
        }
        else {
            pop @loops;
        }
    }
}

use 5.010;
use strict;

my %ops = {
    "+" => sub { say "+ op encountered" }
};

$a{"+"}->();

use 5.010;
use strict;

my %ops = {
    "+" => sub { say "+ op encountered" }
};

$ops{"+"}->();