8

Day 8: Matchsticks

Picat: Part 1, Part 2

A simple counting puzzle.

Part 1

This one went okay, but I found Picat's pattern matching a bit limited when it came to partial string matching. I wanted to match hex code literals a function head like this:

solve([("\\x" ++ [_,_] ++ X)|XS],C,L) = solve([X|XS],C+4,L+1).

Picat didn't like this, and I had to go with nested list constructors instead, making things uglier:

solve([['\\'|['x'|[_|[_|X]]]] | XS], C, L) = solve([X|XS],C+4,L+1).

Maybe there's a nicer way to express this that I'll discover later.

Part 2

Easier than part 1.

Reflections

• Picat could do with nicer string utilities (e.g. a starts_with or contains function, like Haskell's isPrefixOf and isInfixOf, rather than having to either futz with find or awkward pattern matching.

Error collection

*** error until line 11
'|X]]|XS], C, L) = solve(X,C+2,L+1).

(Syntax error, but what is the message trying to say? I think this one came down to my failing to escape a quote in a character literal.)