[erlang-questions] list comprehensions speed

Thomas Lindgren <>
Tue Feb 25 16:22:45 CET 2014


As a related point, I wouldn't mind if, say, Hipe or that forthcoming BEAM/JIT compiler generated code similar to C for these sorts of functions. (It would at least be quite interesting if someone investigated codegen for tight-ish loops further. MSc thesis, anyone?) 

Basically, less code in C please ...

Best,
Thomas



On Tuesday, February 25, 2014 3:28 PM, Ivan Uemlianin <> wrote:
 
There's also lists:keyfind/3 you could try
>
>  http://www.erlang.org/doc/man/lists.html#keyfind-3
>
>I think the lists are written in C, so they should be fast.
>
>Ivan
>
>
>On 25/02/2014 13:08, Oleg wrote:
>>    Hello.
>>
>> I'm erlang newbie. Don't beat me, please :-), if this question is obvious.
>>
>> I have a list of key-value pairs:
>>
>> A=[{"name1", 1}, {"name2", 77}, {"name3", 33}, {"name4", 234}].
>>
>> What is faster:
>>
>> [ Value || {Name, Value} <- A, string:equal(Name, "name3")].
>>
>> Or:
>>
>> get_value(Key, []) ->
>>    [].
>> get_value(Key, [H|T]) ->
>>    {Name, Value} = H,
>>    case string:equal(Name, Key) of
>>      true ->
>>        [Value];
>>      false ->
>>        get_value(Key, T)
>>    end.
>>
>> start() ->
>>    get_value("name3", A).
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>>
>
>-- 
>============================================================
>Ivan A. Uemlianin PhD
>Llaisdy
>Speech Technology Research and Development
>
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