Re: [Haskell-cafe] Name that function =)

On 12/12/06, Conal Elliott wrote:

This rewrite changes the order of execution. The old version did all of the putDirs and then all of the renameFile calls. The new one interleaves putDirs & renameFile calls. In general, ">>" is not commutative, though in this case you may be as happy with either order. - Conal

Right. That's really why I wanted to change it. It should do both actions for each element in one pass over the list.

On 12/12/06, Bryan Burgers wrote:

...

Before we get too far down the obfuscation road, I'd like to offer what I think is more readable than a liftM2 solution:

mapM_ (\p -> putDirs p >> uncurry renameFile p) pairs

I haven't tested it, but I hope that does the same thing. To me, this explicitely shows what each is doing, moreso than with a point-free 'foo' combinator.

The way my mind worked to get to this solution:

mapM_ putDirs pairs mapM_ (uncurry renameFile) pairs

==>

mapM_ (\p -> putDirs p) pairs mapM_ (\p -> uncurry renameFile p) pairs

==>

mapM_ (\p -> putDirs p >> uncurry renameFile p) pairs

Is that a reasonable solution?

That works too. I don't know if I consider the liftM2 solution obfuscated yet, but you're right, it could be leaning that way. Thanks for the alternative suggestion. -- Lou.