the first line says that 'fname' is a function which takes a list and returns a string. the list is of type '[([Char],a)]'. this means that it's a list of ([Char],a)s. these are pairs of [Char]s and as. a [Char] is a string (a string is a list of characters) and an a is a something -- anything you want.
the second line tells you the value of fname when its argument list is empty ([]). the result in this case is the string "Result_Blank". the third line tells you what to do when the input is not empty. when you have a non-empty list, it's composed of a head and a tail, written (head:tail). since our list is of pairs, the head has the form (a,b). putting this together, we have that the list is of the form ((x,xs):ys). here, x is our a, xs is our b and ys is the tail. (x,xs) is our head. it then says that the result of this is just the value 'x'. this is simply the [Char] part (the first half) of the first pair in the list. HTH - Hal -- Hal Daume III | [EMAIL PROTECTED] "Arrest this man, he talks in maths." | www.isi.edu/~hdaume > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Matthew Morvant > Sent: Thursday, August 28, 2003 8:44 AM > To: 'Haskell ([EMAIL PROTECTED])' > Subject: New to Haskell > > > Hello, > I am very new to haskell. I was hoping someone could > explain something > to me > > fname :: [([Char],a)] -> String > fname [] = "Result_Blank" > fname ((x,xs):ys) = x > > What exactly [use little words :-)] does this do? > _______________________________________________ > Haskell-Cafe mailing list > [EMAIL PROTECTED] > http://www.haskell.org/mailman/listinfo/haskell-cafe > _______________________________________________ Haskell-Cafe mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell-cafe
