[Haskell-beginners] Are these soloutions all valid and a good use of Haskell

Leza Morais Lutonda leza.ml at fecrd.cujae.edu.cu
Mon Nov 10 18:52:21 UTC 2014

Hi Roelof,

On 10/11/14 10:10, Roelof Wobben wrote:
> No problem .
> Im strugelling to make acc work.
> I try to say that if the input list has only 1 item the outcome is the 
> head of that list.
> But doing
> acc = Just (head a)  or doing acc = Just (head acc) gives both that 
> acc or a is not in scope
The `a` in the type signature `acc :: a -> Maybe a -> Maybe a` is not a 
variable name, it is a type.
> also doing acc x = Just (head x) gives a error messages that the types 
> are not matching.
:t Just (head x)
Maybe a

:t acc x
Maybe a -> Maybe a

So, the compiler is right!

> Roelof

Leza Morais Lutonda, Lemol-C
Electronic and Telecommunication Engineer
Software Development and Architecture Enthusiast

50 Aniversario de la Cujae. Inaugurada por Fidel el 2 de diciembre de 1964  http://cujae.edu.cu

More information about the Beginners mailing list