If your functions have the same type, then you can easily collect them
in a data structure, say list, and fold that.
For example:
function :: String -> (String -> String)
function "f1" = f1
function "f2" = f2
function "f3" = f3
runAUserSpecifiedComposition :: String -> F
runAUserSpecifiedComposition = foldl (.) id . map function . words
runAUserSpecifiedComposition "f1 f2 f3" should be equal to (f1 . f2 . f3) now.
On 24 August 2011 13:35, dokondr
Hi, What is the Haskell way to compose functions in run-time? Depending on configuration parameters I need to be able to compose function in several ways without recompilation. When program starts it reads configuration parameters from a text file. For example, I have three functions, f1, f2, f3, each doing some string processing. I need to support two configurations of string processors :
if param1 then sp = f1 . f2 . f3 else sp = f1 . f3
I'd like to avoid 'if' somehow and instead use some declarative way to specify code to run in external configuration file. In other words I need some easy tools to create mini DSLs without all the efforts usually involved with implementing full-blown DSL.
Thanks, Dmitri
_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe