[erlang-questions] Why lists:dropwhile() didn't return the expected result?

t ty <>
Thu May 1 13:29:11 CEST 2008


dropwhile docs says "Drops Elem while Pred return true and returns
remaining list"

and in your example

K(1) = false
i.e. the first element dropwhile encounters Pred return false and the
remaining list (which is the whole list) is returned.

Look into lists:takewhile/2 instead.

t



On Thu, May 1, 2008 at 6:42 AM, catsunny <> wrote:
> Hello,
>  Hope I am not ask silly questions. I am new to erlang. So it's probably my
>  mistake.
>  The following is what I did:
>
>  13> K=fun
>  13>     (X) when X>4 ->
>  13>          true;
>  13>     (X) when X==4 ->
>  13>          true;
>  13>     (X) when X<4 ->
>  13>          false
>  13> end
>  13> .
>  #Fun<erl_eval.6.13229925>
>  14> lists:dropwhile(K,[1,2,3,4,5,6,7,8]).
>  [1,2,3,4,5,6,7,8]
>  15> K(1).
>  false
>  16> K(55).
>  true
>
>  At prompt line 14, I hope the return value to be [1,2,3], but it's
>  [1,2,3,4,5,6,7,8]. Why?
>
>  Thanks.
>  Catsunny
>  2008-05-01
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