Twan van Laarhoven wrote:
Josef Svenningsson wrote:
Hi all,
It is becoming increasingly popular to import Control.Arrow just to get access to the functions &&& and *** specialized to the function arrow. I propose to add the specialized version of these two functions to Data.Tuple which is more logical thing to import if you wish to have functions operating on tuples.
Other functions for which Arrow is often unnecessarily used are first and second
first :: (a -> b) -> (a,c) -> (b,c) first f (x, y) = (f x, y) second :: (a -> b) -> (c,a) -> (c,b) second f (x, y) = (x, f y)
I think these should be added as well. I don't really like these names, but they are the names from Control.Arrow. The problem is that 'fst' and 'first' are essentially the same, but they do different things. Maybe 'mapFst' or 'updateFst' is a better name.
'onFst' and 'onSnd' look nice to me: onFst (+1) (1,'a') ==> (2,'a') Cheers Ben