Case as to If?

[Grok]

There's nothing natural about If statements.

[Skywing]

In a language like C or C++ that imposes strict requirements on what you can have for a switch (analog of "select case"), a multiple-selection flow structure is generally much faster than a series of if statements.

This is because the compiler can often optimize the multiple-selection structure to use only one or two compares, despite there being multiple outcomes, something that generally isn't possible with if statements.

Consider the following:

Code Select Expand


int i;
// ...
switch(i) {

case 0: // ...
break;
case 1: // ...
break;
case 2: case 3: //  ...
break;
case 4: // ...
break;

}


The compiler can be clever and turn this into a table lookup that goes something like this in pseudocode:

handlerindex = handlerindextable;
handler = handlertable[handlerindex];
goto handler;

With this kind of optimization, there is no need to individually test for outcomes.

Note that because VB allows you to put almost anything into a select case construction, this optimization is probably not as applicable, so the speed difference between an if and a select case may not be as drastic as the speed difference between an if and a switch in C or C++.

[hismajesty]

I was told by "professionals", that if statements were naturally quicker, is this true?

AFAIK no. When I first started in VB I did If statements for everything and was told that Case is better. Where exactly did these "professionals" work? Also, I may be wrong (and probably am) so I too would like to know.

[Spht]

I was told by "professionals", that if statements were naturally quicker, is this true?

AFAIK no. When I first started in VB I did If statements for everything and was told that Case is better. Where exactly did these "professionals" work? Also, I may be wrong (and probably am) so I too would like to know.

Work with the logic which I posted and you'll be fine.

[Adron]

There's nothing natural about If statements.

They sound like natural language!

[Etheran]

I thought polymorphism was invented to rid the world of the cases!  

[hismajesty]

I was told by "professionals", that if statements were naturally quicker, is this true?

AFAIK no. When I first started in VB I did If statements for everything and was told that Case is better. Where exactly did these "professionals" work? Also, I may be wrong (and probably am) so I too would like to know.

Work with the logic which I posted and you'll be fine.

Aye, so I was correct?