On Fri, Mar 12, 2010 at 10:29 AM, Johannes Waldmann
Well, meaningful identifier names is nice, but I think here we have a case of the code smell "type info embedded in the name". Strictness of a function should be expressed in the function's type instead. But that seems impossible with Haskell at the moment. (At best, we can express strictness of constructors?) Hence we have "underspecified" behaviour:
Prelude Data.List> :t foldl' foldl' :: (a -> b -> a) -> a -> [b] -> a
Prelude Data.List> :t foldl foldl :: (a -> b -> a) -> a -> [b] -> a
Even if we had a syntax to express that the function is strict, wouldn't we still need two distinct function names for the strict and lazy case ? In that case, some sort of convention on naming is nice, because if I want to change a function to its strict version, I know there's a good chance it's the one that ends with a ' David.
and need to resort to the awkward workaround via naming conventions.
Of course Haskell implementations do have some kind of strictness information (e.g., in ghc interface files), so it's not impossible to define some kind of annotation system.
Although I did not check what the compiler's strictness info is for foldl and fold' - and what was actually needed (at the source level). The current textual definition (Data.List API docs: "foldl' = a strict version of foldl") is not too precise, either.
Well, I guess there's a huge design space. But it's a huge problem (describing/controlling the behaviour of lazy programs).
Best - J.W.
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