From: Brett Simmers <bsimmers@...>
Date: 2007-08-03T01:30:58+09:00
Subject: Re: sytnax

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Phlip wrote:
> Shai Rosenfeld wrote:
>
>   
>>> var = { 1 => 'one', 2 => 'two', 3 => 'three' }.fetch(number, 'else')
>>>       
>> nice! :)
>>
>> any lead to which one is faster?
>>     
>
> D'OH!
>
> (There was just a big discussion on Ruby performance, or lack thereof.
> Google "Performance diffrence between ifs and case", and learn A>
> premature optimization is the root of all evil, and B> you can profile
> each system with unit tests and Benchmark library.)
>
>   
In this case it's hash lookup vs. case scanning which is significantly 
different than if vs. case.  Since hash lookups should be O(1) and 
scanning all the clauses of a case statement is O(n), using the hash 
would in theory be faster.  However, if you're only doing it a couple 
times and there's a small number of cases, the overhead of creating the 
Hash might make the case statement faster.  In fact, constructing the 
hash the first time will be at least O(n), so the hash method will 
almost definitely be slower if you only do the lookup once.  Of course, 
as you said, the best way to find out is to benchmark it yourself. 

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