On Wednesday 11 July 2007, Hugh Perkins wrote:
Well, there's a fundamental reason it wont work for Haskell: we dont actually define the names of the parameters to the function!
Have a look at the function above, the function is defined as:
testunique' :: Eq a => [a] -> [a] -> [a] testunique' [] elementssofar = [] testunique' (x:xs) elementssofar
There's an agreement here that the second parameter is called "elementssofar"... but only because I was consistent in my naming in this example. What if we had multiple constructors for a particular type?
The first argument has no obvious naming at all.
We could do things like write it in comments:
testunique' :: Eq a => [a] -> [a] -> [a] -- testunique' :: remainingelements -> elementssofar -> uniqueelements testunique' [] elementssofar = [] testunique' (x:xs) elementssofar
... but we all know that no-one bothers writing comments, and certainly never maintaining them, and in any case this is becoming insanely difficult to read.
I dont have a solution, apart from using C# for production programming ;-) , but things like this are really important to solve in any "mainstream" version of Haskell.
One could put up the Haddock doc-comment. Or, say, one could extend Haddock to support parameter names: testunique' :: Eq a => [a] -- ^ $list List of elements to test -> [a] -- ^ $elementssofar List of elements seen thus far -> [a] -- ^ List of unique elements in 'list'. No patch forthcoming from this corner, though. Jonathan Cast http://sourceforge.net/projects/fid-core http://sourceforge.net/projects/fid-emacs