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

[Roelof Wobben]

Thanks all,

I will try to make a fold solution as soon as I see that functional 
explained in the learnyouahaskell.

Roelof


Frerich Raabe schreef op 10-11-2014 11:43:
> On 2014-11-10 11:16, Karl Voelker wrote:
>> On Mon, Nov 10, 2014, at 01:50 AM, Roelof Wobben wrote:
>>> What do you experts think of the different ways ?
>>
>> 2 and 4 are quite similar, and both fine. 3 is not so good: guards
>> provide weaker guarantees than patterns, and head and tail are partial
>> functions.
>
> In addition to what Karl wrote, I'd like to suggest not using the 
> semicolon all the time -- it's not needed and just adds noise.
>
>> All three implementations have in common that they do their own
>> recursion. It would be a good exercise to try implementing last as a
>> fold - in other words, letting the standard library do the recursion for
>> you.
>
> Right - I suggest trying to express the problem with the most abstract
> function first, then consider using a fold, then use manual recursion. in
> your particular case you could exploit that for non-empty lists, getting
> the last element of a list is the same as getting the first element of
> a reversed list (and there are ready-made functions for reversing a list
> and getting the first element of a list).
>