Ilya Tsindlekht <[EMAIL PROTECTED]> writes: > On Sat, May 19, 2007 at 09:16:46PM +0100, Jon Fairbairn wrote: > > Ilya Tsindlekht <[EMAIL PROTECTED]> writes: > > > By definition, tail recursive function is recursive function in which > > > the value returned from a recursive call is immediately returned without > > > modification as value of the top-level invocation, which is true for > > > foldl defined as above. > > > > Sure. Did I say otherwise? > Sorry, I thought you were saying foldl is not tail-recursive. I must > have not read your message carefully enough, mea culpa.
No worries. I was, in fact, saying that in a lazy language more things are tail recursive than you might expect, owing to the possibility of defining choice functions other than if and case. One might even argue that the question of whether something is tail recursive (in effect) depends on the context: > down 0 = [] > down n = n:down (n-1) is clearly not tail recursive: the tail call is to (:), but if the context only ever applies either head or tail, (:) is effectively a choice... > silly [] = [] > silly (x:xs) = silly xs clearly is, now silly (down n) only ever applies tail to the conses, so no state builds up, so the combined effect of the two functions is as if they were tail recursive. -- Jón Fairbairn [EMAIL PROTECTED] _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
