Re: Duda IF ?

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#171

From: Pascal J. Bourguignon
Date: Mon, 24 Aug 2009 11:56

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ELfun <virtial.disco@gmail.com> writes:
> OK, es lo que quer�a saber las diferentes alternativas, pero me surge
> otra pregunta de las tres posibles soluciones cual es la que genera
> menos c�digo maquina por el compilador?..

Depende de los valores con que comparas, y del compilador.

Si tienes valores agrupados:

    if(a==1){
        ...
    }else if((a==2) or (a==3)){
        ...
    }else if(a==4){
        ...
    }else{
        ...
    }

entonces con un switch el compilador podra generar una tabla de
saltos, basicamente algo como:

   if((a<1)or(a<4)){
      ...
   }else{
      (tabla[a])();
   }

Pero con valores como la que muestras, lo mas probable es que el
compilador generara exactamente el mismo codigo con un if o con un
switch.

Lo mejor es comprobarlo t� mismo, con:

       g++ -S -o file.s file.c++
       cat file.s

-- 
__Pascal Bourguignon__

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From: pjb@informatimago.com (Pascal J. Bourguignon)
Date: Mon, 24 Aug 2009 13:56:07 +0200
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