[erlang-questions] splitting

[Chandru]

On 03/03/2008, Balathasan Sayanthan <bsayanthan@REDACTED> wrote:
> Hi ,
>
> I am trying to write a decoding logic to decode a list which has a
> predefined separator ( eg.  tab). But  the  distance at which the  separator
> will occur from the start of the list is unknown. I want to extract all the
> values before the separator into one list and the rest of the list into
> another, what would be the best way of doing this in Erlang?
>
> for example if the program is given a list like [ 23, 34,  9, 34, 78, 90, 9,
> 10, 34 ]
>
> I want this to  be split into [23, 34] , [ 34, 78, 90, 9, 10, 34] using 9 as
> the separator(the point at which will occur is a variable and aslo there
> might be multiple occurances of it).
>
> Am I supposed to use the string:tokens(string, substring), but is there a
> more efficient way of doing it in Erlang?
>

You can quite easily write a function to do this.

split_at(List, Split_char) ->
    split_at(List, Split_char, []).

split_at([Split_char | T], Split_char, Acc) ->
    {lists:reverse(Acc), T};
split_at([H | T], Split_char, Acc) ->
    split_at(T, Split_char, [H | Acc]);
split_at([], _, Acc) ->
    {lists:reverse(Acc), []}.

Alternatively, have a look at lists:splitwith/2

cheers
Chandru