On Tuesday, February 5, 2002, at 02:16 , Jeffrey R Lewis wrote:
> On Tuesday 05 February 2002 09:40 am, Brian Berns wrote: >> I am new to functional programming and teaching myself Haskell. The >> canonical Haskell "fib" function (e.g. as presented in the "Gentle" >> tutorial) is: >> >> fib = 1 : 1 : [ a+b | (a,b) <- zip fib (tail fib) ] >> >> This seems, to be polite, a bit overly complex. By comparison, here >> is a simpler version: > > As an aside, here's a nicer way of writing the stream version of fib: > > fib = 1 : 1 : [ a + b | a <- fib | b <- tail fib ] > > This gets rid of the distraction of the zip and the pair, letting you > see > the simple structure of the definition more clearly. > > This, however, is not Haskell 98 (the use of multiple generators > separated > by `|'). But it is supported by both GHC and Hugs (using flag -98). > See > the sections in the user manuals under `parallel list comprehensions'. > > --Jeff > http://www.haskell.org/mailman/listinfo/haskell And while you're at it start the sequence with 0 : 1 : ... so that it has the nice property that: gcd (fib !! m) (fib !! n) == fib !! (gcd m n) -- Frank Seaton Taylor [EMAIL PROTECTED] _______________________________________________ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
