Miscellany

#!/usr/bin/perl
# Example parser.
# Parses thingies.
# eg:
#   thingy {
#       foo
#       bar
#       baz
#       thingy {
#           some
#           sub
#           thingy
#           filler
#           thingy {
#               and some more crap
#           }
#       }
#   }

use strict;
sub peek_tok
{
    my ($toks) = @_;
    return $toks->[0]
}
sub next_tok
{
    my ($toks) = @_;
    return shift @$toks;
}

sub parse_thingy
{
    my ($toks) = @_;
    my $tok;

    print "Entering thingy\n";
    # don't swallow "thingy" unless we're actually parsing
    # a thingy block
    if (peek_tok($toks) ne "thingy") {
        $tok = peek_tok($toks);
        print "got ''\n";
        return "failure";
    }
    # ditch "thingy" token
    next_tok($toks);
    if (next_tok($toks) ne "{") {
        die "Expected '{' in thingy block";
    }
    while (($tok = peek_tok($toks)) =~ /[a-zA-Z0-9]+/) {
        if ($tok eq "thingy") {
            parse_thingy($toks);
        } else {
            print "this thingy has $tok\n";
            next_tok($toks);
        }
    }
    if ($tok ne '}') {
        die "Unrecognized token $tok in thingy, expected '}'";
    }
    print "Exiting thingy";
    return "success";
}

# vars for a file
my $term = $/;
my $tokens;
my $fc;
my @split_input;
# slurp in a file
undef $/;
$fc = <>;
$/ = $term;

# split into tokens and take an array reference to the returned value
@split_input = split(/[\t \n]+|([\'\(\)])|(".*?")/, $fc);
# delete empty fields that split sometimes puts in.
for (@split_input) {
    if (/^$/) { next; }
    push(@$tokens, $_);
}
print parse_thingy($tokens), "\n";