Switch vs. If/Else
I believe that some compilers will optimize larger switches into a search tree (binary, I believe), which on average will be faster that an if/else.
quote:Original post by CaptainJester
A switch/case statement is exactly the same as an if/else set.
Perhaps if you're programing in (Object) Pascal or VB - we like C/C++ here
A switch uses a jump table - one of the requirements of the C switch is that each case be a const integral value to allow this implmentation. If the cases change at run-time (non-const), you need code there to do the check.
NULL is a macro, and that probably has something to do with why the case rejects it. Just use 0.
Switches are preferred to chained-if's. And virtual functions are preferred to switch blocks. There are cases when using the former makes more sense (if speed is paramount, use the switch). If extensiblity and solid architecture is important, use virtuals. If the cases are nebulous but unchanging, use chained if's.
Edited by - Magmai Kai Holmlor on January 30, 2002 9:12:07 PM
Edited by - Magmai Kai Holmlor on January 30, 2002 9:12:23 PM
quote:A switch uses a jump table
This is stated too strongly.
A switch *can* be optimized into a jump table. It requires certain conditions to hold true -- most importantly, the values should all be fairly close and fairly small.
If not, it may get turned into chained if/elses, or potentially a binary tree search.
quote:Switches are preferred to chained-if''s. And virtual functions are preferred to switch blocks.
It doesn''t seem immediately obvious as to why you would use a switch instead of a virtual function, nor how you might replace a switch with a virtual function, unless perhaps you''re doing something vile with RTTI.
I think VB can do case statements with strings, not just ints...feel free to correct me if I''m wrong
quote:Original post by Magmai Kai Holmlor
Perhaps if you''re programing in (Object) Pascal or VB - we like C/C++ here
I prefer C/C++ too. Back when I was taught C in college(back in the stone ages), we were taught that switch/case were treated the same as if/else by the compiler, except for certain restrictions on the switch/case. I took those classes back in 1989, so maybe things have changed since then. I haven''t kept up that much on it until now. I just started getting back into it.
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Make it work.
Make it fast.
"Commmmpuuuuterrrr.." --Scotty Star Trek IV:The Voyage Home
<C# Plug>C# does switches on constant strings</C# Plug>
Once there was a time when all people believed in God and the church ruled. This time is called the Dark Ages.
Once there was a time when all people believed in God and the church ruled. This time is called the Dark Ages.
quote:Original post by Arild Fines
<C# Plug>C# does switches on constant strings</C# Plug>
So does VB.
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