[Haskell-beginners] Re: Integer factorization

Colin Paul Adams wrote:

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"Heinrich" == Heinrich Apfelmus writes:

Heinrich> Abstraction is the one driving force for very short Heinrich> names. For example, take the definition of foldr

Heinrich> foldr f z [] = z foldr f z (x:xs) = f x (foldr f z Heinrich> xs)

Heinrich> Since this function is polymorphic, so f , z and the xs Heinrich> can be anything, using more "descriptive" variable names Heinrich> is simply not possible; the key point of fold is its Heinrich> generality.

Wouldn't unit be a better descriptive name than z?

I have never heard of a unit in relation to fold , I'm afraid. Monoids and groups have units, as do physicists and a few other mathematical structures. While z is indeed quite often the unit of a monoid, for instance in sum = foldr (+) 0 product = foldr (*) 1 concat = foldr (++) [] it doesn't have to be the unit of a monoid. Regards, apfelmus -- http://apfelmus.nfshost.com