User talk:Sarabander

Hello! (and a note about that functor law)
A (late) welcome to the Haskell Wikibook, and thanks for your corrections there! I have just rejected on of your edits to the Functor chapter, in which you had changed the first functor law to. It is pretty much a matter of style, but laws such as the functor laws tend to be written point-free (at least if point-free doesn't make the expression too ugly/complicated), to emphasise that the interesting things it specifies happen to the function (i.e. we tend to look at  as a   function, which promotes functions to the  ). A more compelling example, perhaps, is the second law.Pointfully written, it looks like this

or this

Both forms, specially the second, obscure a bit the essence of the second law - that  preserves function composition, which shows up very clearly when writing it point-free:

Feel free to keep fixing as many bugs as you feel like, and to ask questions about the text in the talk pages. Thanks again, and cheers, Duplode (discuss • contribs) 16:25, 1 July 2015 (UTC)


 * Thanks for your explanation! The point-free style indeed is better. I was momentarily confused by the (==) used to express the identity of functions. How silly of me, as I just recently read The Annotated Turing by Petzold and watched a Haskell lecture by Jürgen Giesl, where they explicitly said that comparing two functions is undecidable. So the (==) relation here stands for mathematical identity, not Haskell equality.


 * Actually, using  in laws can be confusing indeed. I'm changing it to plain old  . Duplode (discuss • contribs) 21:29, 1 July 2015 (UTC)