Jacque,
I think what you are discovering is that "it depends". I noticed a
couple of things with your example:
1) Your switch conditions are all expressions that need to be
reevaluated in every iteration (as opposed to constant value). This
effectively kills the switch statement's ability to "jump" to the
correct result - since it has to reevaluate the "jumps" every time
through. Try throwing in string constants and switch should start
gaining.
2) 3-4 possible results is probably around the break-even point (in
general). But every extra condition will typically cause a gain on
the switch side.
I think the basic lesson though is that there is no general answer.
It depends a lot on your data. For example, even the same if
statement can be written to be 10 times faster or slower depending on
the data. Suppose your first if statement passes 99% of the time, as
opposed to failing all tests 99% of the time.
My general thoughts:
* Use switch statements when you have 3 or more constant expressions
(or may need to add more in the future)
* Use switch statements if you need the "fall through" logic (by
omitting break statements). Sometimes this leads to more elegant
looking code.
* Use if statements when you have complex expressions and can predict
to some degree which conditions will pass/fail most of the time
* If speed is not an issue, use whichever one makes the most sense to
you
Scott Kane wrote:
----- Original Message ----- From: "J. Landman Gay"
<[EMAIL PROTECTED]>
I read somewhere a long time ago that switch statements run
faster than if/else. I think it was a general comment rather than
specifically related to Revolution programming but it was so long
ago I can't recall. Does anyone know if it is true for Rev scripts?
I haven't timed it - but if it's read by the engine in the same
manner other programming languages handle it then it would be
faster as any subsequent conditions are skipped because once the
case statement (switch statement) is met the compiler knows not to
proceed - as opposed to if/then/else etc where the entire handler
is evaluated in full.
I remember reading that Rev doesn't evaluate the entire if/else, so
I'd think it would be about the same as switch. But lookee here, I
did a test, with surprising results:
on mouseUp
put 100000 into tRepeats
put the milliseconds into tstart
switchTest tRepeats
put the milliseconds - tstart into item 1 of tTimes
put the milliseconds into tstart
ifTest tRepeats
put the milliseconds - tstart into item 2 of tTimes
put tTimes
end mouseUp
on switchTest pRepeats
put 1 into tRep
repeat pRepeats
switch tRep
case tRep > 10000
put tRep into x
break
case tRep > 5000
put tRep into x
break
case tRep > 2000
put tRep into x
break
default
put tRep into x
end switch
add 1 to tRep
end repeat
end switchTest
on ifTest pRepeats
put 1 into tRep
repeat pRepeats
if tRep > 10000 then
put tRep into x
else if tRep > 5000 then
put tRep into x
else if tRep > 2000 then
put tRep into x
else
put tRep into x
end if
add 1 to tRep
end repeat
end ifTest
The "if/else" is 4 to 5 times faster. <blink> Is my test accurate?
--
Jacqueline Landman Gay | [EMAIL PROTECTED]
HyperActive Software | http://www.hyperactivesw.com
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