http://qs321.pair.com?node_id=1068418

in reply to Hash Uninitialized Values Error

Ok, I looked at the code up, down and sideways, then started refactoring common code and realised that half the logic vanishes if the two sets of statements are stored in one structure. I also noticed a bunch of make work creating a transient numbered set of data so I eliminated that. Then the code seemed to simplify down to the point where I could see what was going on. Here's the result:

```use strict;
use warnings;

if (!@ARGV) {
print <<HELP;
Hi. This is the Lee-Hardy Conclusion Calculator.
Given a list of statements on the command line using the syntax "p
+ -> q" I
will deduce the correct conclusion to be made using basic logic an
+d the
chain rule.

- may be used for negation
q's can not be duplicated
HELP
exit;
}

LHCC(parse(@ARGV));

sub LHCC {
my (%all) = @_;
my @Conclusion;
my @alternate;

foreach my \$testKey (keys %all) {
my @candidate = (\$testKey);
my \$nextKey = \$testKey;

while (\$nextKey) {
\$nextKey = \$all{\$nextKey};
push @candidate, \$nextKey;

last if ! exists \$all{\$nextKey};
}

if (scalar @candidate > scalar @Conclusion) {
@Conclusion = @candidate;
} elsif (scalar @candidate == scalar @Conclusion) {
@alternate = @candidate;
}
}

print join ' => ', @Conclusion;
print "\nor\n";
print join ' => ', @alternate;
print <<RESULT;

In other words: \$Conclusion => \$Conclusion[-1]
or: \$alternate => \$alternate[-1]
RESULT
}

sub parse {
my %all;

for my \$statement (@_) {
my (\$p, \$q) = \$statement =~ /(\S+)\s*->\s*(\S+)/;
\$all{\$p} = \$q;
\$_ = /^-(.*)/ ? \$1 : "-\$_" for \$p, \$q;
\$all{\$q} = \$p;
}

return %all;
}
```p => f => c => -b => -g