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 <doko...@gmail.com> wrote: > 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 > > _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe