[erlang-questions] guards

Dave Pawson <>
Sat Jul 25 10:46:55 CEST 2009

2009/7/25 Hynek Vychodil <>:
> On Sat, Jul 25, 2009 at 4:50 AM, Dave Pawson <> wrote:
>> filterHelper(Lst,Int,Result) when ((length(Lst) == 1) and
>> (lists:nth(1,Lst) =< Int)) ->
>>    [lists:nth(1,Lst) | Result];
> It is little bit overcomplicated version of
> filterHelper([X], Int, Result) when X =< Int -> [X|Result];

Mmm. Thanks... I think :-)
(I'm trying to learn!)

Does that check for a list length of 1?
As well as the value being <=  (who the heck chose =<
that is a real kludge!!!) Int?

> and also lists:nth(1,L) is equivalent of hd(L) which can be used in guards
> but in most of time use list decomposition in pattern match is more
> effective way to do it.

Ah! Didn't know about hd(L).
   Is there a quick reference chart for Erlang Bofs, perhaps the common
  module functions?
  Seems its something to fight going into any language!

Thanks Kynek.

Dave Pawson
Docbook FAQ.

More information about the erlang-questions mailing list