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I'm just wondering how many ifs people use before they use switch instead. I have an old tile game that I'm redoing the engine on now that I'm more experienced, and I have to test for 12 different tiles with a movement in each direction. So what's the max ifs you should have before a switch is more effecient, three, four? Also, would it matter what kind of coding your putting inside of the cases to determine what would be better?
switch?? can you point me to a switch tutorial i dont know what you mean by switch??
i don't think switch is faster or slower so it doesn't really matter, if you don't put breaks in your switches then it could get slow. Its just a better way to look at code (i think).
Sorry IP cant help you, but in responce to Alex, just use flash help (open up flash, click on help found on the toolbar, click on flash help and search for "switch statement") and switch will be explained there.
Viza
I'm not sure if has an effect on speed, but I would do it for about 5 cases. And those cases should be very brief with no nesting. Mostly just to make my code readable. Also I always think if you're using cases you could have probably done something with arrays instead.
In bytecode, there's no difference between a series of if - else if and a switch statement. When publishing, a switch is converted to if - else if equivalent using a local variable. For clarity, it's a good idea to use switch though. But it's not drastically faster. This means it's still important to place the most likely cases at the top to speed it up.
I've got to admit, I've never used switch once.
The quickest way of the lot is to do it this way:
As a complete alternative you could just call a function directly if you're having a different outcome for each tile, egCode:if(a==1){
} else {
if(a==2){
} else {
if(a==3){
}
}
}
Squize.Code:var tileAttribute=_map[ypos][xpos][0];
var call=this["func"+tileAttribute];
call();
....
function func0(){
}
function func1(){
}
Malee - you mean breaks are not necessary?
This.Alex - an even easier way to find help topics is to type the part or thing you want in the actual code window so it changes color, letting you know it's a built in thing. Then right click on it and click view help.
Strille - That's really good to know. Thanks for the input.
Squize - I thought it was deemed bad practice to use a lot of if's in a game, or at least I remember seeing that somewhere. I did however like the idea of calling a function for each one.
Good practise and speed issues hardly ever agree :)
Squize.
If memory serves me right, break is only necessary when you want to stop evaluating the remaining cases ... (been long time since C class...)Quote:
Originally Posted by ImprisonedPride
I use switch if I'm evaluating a single variable, sometimes you cant get around nested ifs:
if(x && y)
{
if(z || x)
{
//blah
}
}
But if I'm evaluating the same variable, I'll switch if its more than an if else.
ok thanks do you think switch is worth knowing or can if functions do everything that switch can do??
You can do some things in switches which are easier than ifs
code:
switch(a)
{
case 0:
//case 0
break;
case 1:
//case 1
break;
case 2:
//case 2
case 3:
//case 3
break;
}
In this example, if 'a' is 2, then it executes cases 2 and 3, which would be a pretty messy if statement with repeated blocks of code.
breaks on
out put:Code:#include<iostream>
// my example
void main()
{
xix=1;
switch(xix)
{
case 1:
cout<<xix<<endl;
break;
case 2:
cout<<xix<<endl;
break;
case 3:
cout<<xix<<endl;
break;
case 4:
cout<<xix<<endl;
break;
}
cin>>xix;
}
breaks offCode:1
outputCode:#include<iostream>
//note the same code just without breaks
void main()
{
xix=1;
switch(xix)
{
case 1:
cout<<xix<<endl;
case 2:
cout<<xix<<endl;
case 3:
cout<<xix<<endl;
case 4:
cout<<xix<<endl;
}
cin>>xix;
}
switch statements are mostly used on error massages. like this.Code:1
2
3
4
Code:#include<iostream>
//note the same code just without breaks
void main()
{
errorcode=0;
while(errorcode<10)
{
errorcode++;
switch(errorcode)
{
case 1:
cout<<errorcode<<" windows error 101"<<endl;
break;
case 2:
cout<<errorcode<<" windows blue screen of death"<<endl;
break;
case 3:
cout<<errorcode<<" windows time for a mac"<<endl;
break;
default:
cout<<errorcode<<" windows it happens"<<endl;
break;
}
cin>>errorcode;
}
Works the same in Flash, it's the standard case for switch statements.
If that's true, than I guess it's what I want in my case, because I'm only checking to see what frame the tile is. Once I found it, there'd be no reason to keep checking because the switch is in a function that runs only on keypresses anyhow.Quote:
Originally Posted by Ray Beez
its amazing how little actionscript i know (just learned :P)
if you ask me, all versions seem like they act at the same speed
personaly, i would avoid several conditions and whatnot all in one place completely, and try to find shortcuts instead
instead of:
i think it would be a tad bit easier to:Quote:
function asdf(variablehere){
switch(variablehere){
case 1:
trace("1");
break;
case 2:
trace("2");
break;
case 3:
trace("3");
break;
default:
break;
}
}
teehee, good thing i learn fast, otherwise id be left cluelessQuote:
function asdf(variablehere){
if(variablehere<=3){
if(variablehere>=1){
trace(variablehere);
}
}
}
you could write it:
code:
function asdf(variablehere){
switch(variablehere){
case 2:
case 3:
trace(variablehere);
}
}
The point is, switches have their uses, you generally wouldn't use one in this situation.
I think someone mentioned this, but I think I just do it habitually because it really neatens up the coding structure, though I suppose nested ifs wouldn't be anymore disorganized. Less }'s I suppose.
you guys are talking like flash nerds lol (no offence) ok so how would i make an object move using switch heres the if one.
if(Key.isDown(Key.RIGHT)){
_root.flashkit._x+=s;
}
how would you turn that into a switch (i gotta know these things a)
You wouldn't.
Alex, it may be possible to do something like:
...but why would you want to do it this way? Using if's is pretty standard for basic UDLR movement.Code:switch(Key.getCode) {
case Key.RIGHT :
case Key.LEFT :
case Key.DOWN :
case Key.UP :
}
movement in two lines, no if's
_x += Key.isDown(Key.RIGHT) ? 5 : Key.isDown(Key.LEFT) ? -5 : 0
_y += Key.isDown(Key.DOWN) ? 5 : Key.isDown(Key.UP) ? -5 : 0
Might be useful for a tilebased I'm making... afterall, that's the whole spawn of this thread.Quote:
Originally Posted by mr_malee
i imagine switches are a bit more efficient than if's
that way, you only have to call on the variable once, instead of multiple times
mr_malee: wow, you can write if's that way?
Actually that's more old school than you can imagine.Quote:
Originally Posted by trogdor458
kudos to mr_malee for 2 lined movement.
I under stand how to use this but, where did the
come from, what is it called and where can I learn more about this. Thanks.Code:(condition) ? action : 0;
Quote:
Originally Posted by zervell
?: conditional operator
expression1 ? expression2 : expression3
Instructs Flash to evaluate expression1, and if the value of expression1 is true, it returns the value of expression2; otherwise it returns the value of expression3.
this baby was available in flash 4, so yeah, like ImprisonedPride said, its old school. To learn more just use flash help and go to operators, there's lots of other things as well that you might not know about
nice coding malee so thats how you do it thanks guys for the info. and thanks to you as well improsindpride i think thats ur name well thanks for your help as well.(i will start learning this code now)
Just a bit of warning. More compact code often results in worse performance. For instance,
is quite a lot slower than:Code:_x += Key.isDown(Key.RIGHT) ? 5 : Key.isDown(Key.LEFT) ? -5 : 0
_y += Key.isDown(Key.DOWN) ? 5 : Key.isDown(Key.UP) ? -5 : 0
The second example only perform an addition/subtraction when a key is pressed while the first example always performs it (with zero if no key is pressed). In this case it's probably not a big deal because you probably don't check the keys more than once every frame anyway.Code:if (Key.isDown(Key.RIGHT)) {
_x += 5;
} else {
if (Key.isDown(Key.LEFT)) {
_x -= 5;
}
}
if (Key.isDown(Key.DOWN)) {
_y += 5;
} else {
if (Key.isDown(Key.UP)) {
_y -= 5;
}
}
Not saying it's a good idea, but you can off course also use nested switches, or nest if's inside switches.Quote:
Originally Posted by iopred
You can also do things like this :
Which has been useful to me once or twice, but I can't remember when or why.Code:switch(true) {
case a==b : trace("1"); break;
case a!=c : trace("2"); break;
// ...
}
yeah, it does suck, i wish it would work better, i went through a massive conditional phase not long ago until i found out it has bad speed.Quote:
Originally Posted by strille
unfortunately you tend to have to sacrifice speed for size
technically, if you had every single possible output for a game, and just use gotoandstop, it would be ultra fast would it not?
youll probably prove me wrong, i just know it
The real power of Switch is in making alot of "or" comparisons. ie:
That's a little bit cleaner than doingCode:switch(a)
{
case 4:
case 8:
case 12:
//case 1
break;
case 0:
//case 2
break;
default:
// everything else;
}
Code:if((a==4) or (a==8) or (a==12)){
// case 1
} else if (a==0){
// case 2
} else{
// default
}