[erlang-questions] Strings as Lists
Fri Feb 15 21:54:00 CET 2008
David Mercer writes:
> Out of curiosity, besides as an academic exercise and a point of debate,
> what is the practical use of reversing a string? I've been programming for
> a quarter century and am having trouble remembering when I last needed to
> reverse a string. Search? yes; compare? yes; substitute? yes; modify? yes.
> Just can't think of when I've needed to reverse a string. Is there some
> common protocol that requires you to send Unicode strings in reverse order
> or something?
Many tail-recursive algorithms produce reversed lists, so you need
lists:reverse/1 to put them back again at the end. Typical example:
Rev = to_upper(List, ),
to_upper([H|T], Acc) ->
to_upper(T, [H band bnot 16#20|Acc]);
to_upper(, Acc) ->
Yes, there are other ways of writing to_upper/1.
Yes, I could have put a guard on it.
Yes, I can hear the non-ASCII people grinding their teeth over the band bnot
No, the lists:reverse/1 does not change the big O
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