# Reverse Polish Notation Calculator in Perl6++

Apparently Patrick Michaud, pumpking of rakudo, read my post yesterday and he came up with an even better solition!

I’d read his post if I were you, but here was the code he got it down to (after adding the R meta op :-) ):

```
my %op_dispatch_table = {
'+' => { .push(.pop + .pop) },
'-' => { .push(.pop R- .pop) },
'*' => { .push(.pop * .pop) },
'/' => { .push(.pop R/ .pop) },
'sqrt' => { .push(.pop.sqrt) },
};
sub evaluate (%odt, $expr) {
my @stack;
my @tokens = $expr.split(/\s+/);
for @tokens {
when /\d+/ { @stack.push($_); }
when ?%odt{$_} { %odt{$_}(@stack); }
default { die "Unrecognized token '$_'; aborting"; }
}
@stack.pop;
}
say "Result: { evaluate(%op_dispatch_table, @*ARGS[0]) }";
```

Brilliant!

Posted Tue, Mar 3, 2009If you're interested in being notified when new posts are published, you can subscribe here; you'll get an email once a week at the most.