Robert Dockins wrote:
I'm not sure I understand; why do you think that revealing structure is unsafe?
I don't want that i.e. equal maps yield different results, just because they are internally differently balanced.
I'm hesitant to give "fold" a longer name because I think it should be the first fold a programmer reaches for.
I don't aggree. I immediately made it wrong by my own "toList = fold (:) []" and did not even notice foldr or foldl. The fold for efficiency should be mainly used by library writers. But users I tell: correctness first, efficiency (when needed) later!
In the fairly common case where you have a commutative, associative function (eg (+)), you don't care in what order the function is applied to the elements
These properties are not garuanteed and difficult to track down in the few (but severe) cases it's made wrong.
, and you have fold f z === foldl f z === foldr f z.
I see, foldr and foldl are your safe versions! (I think Jean-Philippe only has a safe "fold" and misses an unsafe one.)
In light of this and previous discussions about folds, I think I will be adding a section to the docs about how to chose an appropriate fold for your application.
At least that plus a warning! Cheers Christian