allong.es

of applyFirst is implicit when the remanining parameters are missing, so we only need applyLast. So makeMapper is called as > let mapperWithAGetter = makeMapper (aGetter) This completes the call to applyLast, so now we have a (fun (x) -> map (x) (aGetter)) Now we only need to bind x. The result is called like this > mapperWithAGetter (aList) IMO, all of this could've been written as: > let makeMapper (aGetter) = fun (aList) -> map (aList) (aGetter) Or: > let makeMapper (aGetter) (aList) = map (aList) (aGetter) Read both as: makeMapper takes aGetter and returns a function which takes aList Notice that everything would be much easiear if map took aFunction as its first parameter: > let map (aFunction) (aList) = ... > let makeMapper = map // duh Remember that partial application is implicit! It would also be easier if applyLast had better syntax, using _ for the missing parameter (the first), as in this Scala-like snippet: > def makeMapper(aGetter: Any => Any): List[Any] => List[Any] = { _.map(aGetter) } (I guess Haskell has some nice syntax for this too, but I don't think F# has anything like this) All of this was not easy to get right, I hope I didn't make any mistake regarding the position and number of parameters.