Hi, in one of my programs, I have to modify individual fields of a pretty large record structure quite frequently. Assume the structure is:
data State = State { foo :: [Int] , bar :: [String] }
Then I'd like to have functions setFoo and setBar, which copy a State but replace the field in question with a given value. This is implemented as:
setFoo :: State -> [Int] -> State setFoo st x = State { foo = x , bar = bar st }
setBar :: State -> [String] -> State setBar st x = State { foo = foo st , bar = x }
Now, defining these helper functions for large records is not what I call an interesting job. Thus I wonder, is there any way to automate this task? I thought about using Template Haskell, but I haven't used it at all yet and am uncertain about how difficult accomplishing this would be. I also thought about using "Data.Generics", which I know better, but the generic approach feels like over-kill for this task. In order to use it, I'd have to re-design my data structure as well. So this isn't too attractive ... Any ideas? Comments? Source Code? :-) Peter