[maxtilford]

Using do-notation is probably cheating, but what do you think of this? (in Haskell):

  do { w <- widgets;
       s <- sprockets;
       l <- locations;
       guard (l `hasInStock` w);
       guard (l `hasInStock` s);
       guard (w `isUsableWith` s);
       return (w, s, l); }

We're trading horizontal space for vertical space. I think it's much clearer than either list comprehensions or plain map/filters. It's the best of both worlds.

[frig]

I like the look of it. Am I correct that the order the statements are in translates into the order things are evaluated in when the code is called?

If eg I edited it to be:

    do { l <- locations;
         w <- widgets;
         guard (l `hasInStock` w);
         s <- sprockets;
         guard (l `hasInStock` s);
         guard (w `isUsableWith` s);
         return (w,s,l); }

Does that force it to go through "location-first" and only check the w and s of (w,s,l) for compatibility if it has already ascertained that w and s are in stock @ l?

[maxtilford]

Yes, that's correct.