[erlang-questions] List to proplist?

Hans Bolinder <>
Mon Nov 3 16:48:05 CET 2008


[Richard Carlsson:]
> Hans Bolinder wrote:
> > [Richard O'Keefe:]
> >> A version of unfold that I prefer is
> >>
> >> unfold(State, Splitter) ->
> >>      unfold(State, Splitter, []).
> >>
> >> unfold(State, Splitter, Acc) ->
> >>      case Splitter(State)
> >>        of []            -> lists:reverse(Acc)
> >>         ; [Item|State1] -> unfold(State1, Splitter, [Item|Acc])
> >>      end.
> 
> I was going to comment on this before, but didn't get around to it.
> Please don't use the return convention above; it is not normal
> Erlang programming style, and introduces an improper list for no
> really good reason. A more traditional return convention would
> use e.g., {Item,State1} | 'none'.

[I answered:]
> Thank you for your comments. We have, however, decided not to modify
> the code provided by Richard O'Keefe.

After some more afterthought, we've decided to withdraw lists:unfold/2
from R12B-5. We feel that it was introduced a bit hastily, and that
the normal procedure for introducing new functionality in Erlang and
supporting libraries should be followed. Therefore an EEP will be
written, giving plenty of time before R13B to collect further comments
and suggestions.

Best regards,

Hans Bolinder, Erlang/OTP team, Ericsson



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