Bug: Compiler Error

[neves]

Why bugs keep following me?

Open a new .fla, go to the first frame and put the follow code:



stop()
(this as MovieClip).play()


We know that AS can be written without semicolon (and I prefer that, since I´m a Ruby developer), but the above example, we must use semicolon after stop
This works:


stop();
(this as MovieClip).play()


It´s obviously a parse error from the compiler. This works too:


stop()
var foo = (this as MovieClip).play()

[FizixMan]

Coincidentally, these work:



stop()
MovieClip(this).play()


stop()
this.play()


stop()
MovieClip(this as MovieClip).play()


stop()
Object(this as MovieClip).play()



stop()
play()

Just use a semi-colon or avoid completely obtuse code.

[dthought]

It is best practice in Flash to use semicolons. Just because you are familiar with Ruby doesn't mean you should try to shoehorn its practices into Flash.

In the same way, you can't always shoehorn English words into other languages just by adding a different spoken accent.

Again, not a bug but bad user code. Sheesh. :P

[Breen]

Again, not a bug but bad user code. Sheesh. :P

I don't see how this is "bad" user code. I admit it's not really usefull nor is it efficient. But in any case, it SHOULD work.

[neves]

I don't see how this is "bad" user code. I admit it's not really usefull nor is it efficient. But in any case, it SHOULD work.

Totally agree with Breen, if the compiler accept "not use of semicolon", it should accept always, that´s logic. Yes, that´s a compiler bug.

And the code is just an example, the real code is (parent as MovieClip).play()

How can I submit to Adobe Team?

[senocular]

It seems the parens are evaluated with all white space prior to the determination of command endings allowing actions like

stop
();
to still work (and there may be better use cases). This, of course, breaks with your example since it expects the return value of stop to be a function call with the argument parent as MovieClip.

I will log it as a bug, but I am not entirely sure it will be considered as one.
(This behavior also existed in AS2)

[Rossman]

Totally agree with Breen, if the compiler accept "not use of semicolon", it should accept always, that´s logic. Yes, that´s a compiler bug.


Yes and no. It is a compiler bug, but not what you think - the bug is that the compiler will not detect missing semi-colons in certain cases. (Not that it should allow missing semi-colons in all cases)

Actionscript dictates that semi-colons terminate every statement/line, just because another language doesn't do that is irrelevant.

[neves]

var foo //works
(this as MovieClip).play()



var foo = 10//doesn´t works
(this as MovieClip).play()


IMHO the compiler should do the follow:
if it find a end of line, the command is done, unless it ends with an "open command" like:
this.
play()

or this

foo(
bar(2, 3)
)

On the above example, the correct behavior should be:
stop() // ok
stop(
)// ok
stop
() // invalid

See? It was just a behavior choice madded by the Adobe Team, but it has a better choice.

[Rossman]

Yeah, that's your opinion alright.

In my opinion:



var foo // shouldn't work, if it does this is a compiler bug
(this as MovieClip).play()


but:



var foo; // should work
(this as MovieClip).play();



Personally I have no problems with the choice Adobe made, because I understand that some languages require certain syntax and others don't.

[FizixMan]

In my opinion, put in semi-colons. :P


Like Rossman said:

Actionscript dictates that semi-colons terminate every statement/line, just because another language doesn't do that is irrelevant.

I feel that the ability to leave out semi-colons is just to assist those graphics artists who need to put in a small tiny script but have no background in programming.

[neves]

I feel that the ability to leave out semi-colons is just to assist those graphics artists who need to put in a small tiny script but have no background in programming.

I agree with the first statement, but say that semicolons are for old school programmers that doesn´t realize that you don´t need semicolons :) New line is already an "end of command" separator. See languages like Python and Ruby :)

If you didn´t agree, put yourself in the following situation. Imagine that never had exists semicolon, in the hole programming life. If tomorrow languages starts to use semicolon, what would you think about it? Sincerely!

[Rossman]

Newline is a terrible statement delimiter. Just because Python and Ruby uses it, doesn't make it right, or good.

Many, many languages use semi-colons and there isn't anything wrong with it. Either adapt or don't use Actionscript, but to waste the Flash development team's time with this....? Crazy.




Let's put this in a different perspective
If newline was a good delimiter, all our text would be like this
It doesn't seem that practical to me
Sorry if you young kids can't handle using good syntax




Let's put this in a different perspective. I think this is much easier to read. Compared to the above it's definitely preferable. Sorry if you young kids can't handle using good syntax.

[neves]

Please, don´t tell me that a code that everyone write like this: (with/or without semicolon, doesn´t matter, each command are on a new line)



var total:Number = 0
for each (var property:XML in myXML.item)
{
var q:int = Number(property.@quantity)
var p:Number = Number(property.price)
var itemTotal:Number = q * p
total += itemTotal
trace(q + " " + property.menuName + " $" + itemTotal.toFixed(2))
}
trace("Total: $", total.toFixed(2))

you prefer to write like this:


var total:Number = 0; for each (var property:XML in myXML.item) { var q:int = Number(property.@quantity); var p:Number = Number(property.price); var itemTotal:Number = q * p; total += itemTotal; trace(q + " " + property.menuName + " $" + itemTotal.toFixed(2))} trace("Total: $", total.toFixed(2));
Thanks to semicolon, we can write code on only one line :) Thanks god for semicolon :)

In true, I´m a multi language programming, and don´t care about semicolon. But I´m a teacher too, and 90% of my students have problems of forgetting semicolons at end of line. But EVERY ONE automatically understand that one command per line is fine :) So, why the need of semicolon, they ask me?

[Rossman]

and 90% of my students have problems of forgetting semicolons at end of line.

Then you should dock them points, it's not exactly the hardest concept they will encounter ;)


So, why the need of semicolon, they ask me?

Why? Because that's how Actionscript works. Plain and simple ;) They would have to learn that discipline in a language with a better compiler, like C (and it's variants), Java, etc. which actually enforces the rules better.

Also, I wasn't saying that people *should* code everything on one line, but there with a specific delimiter (unlike newline) you can if need be.

Understanding the details of a languages syntax is something a good programmer should just do.

[FizixMan]

In true, I´m a multi language programming, and don´t care about semicolon. But I´m a teacher too, and 90% of my students have problems of forgetting semicolons at end of line. But EVERY ONE automatically understand that one command per line is fine :) So, why the need of semicolon, they ask me?



function test(param1:String, param2:Number, param3:Array, param4:Object, param5:Object, param6:Object, param7:Object):String
{

//Logging statement
trace("Test called!"
+ " param1: " + param1
+ " param2: " + param2
+ " param3.length: " + param3.length
+ " param4: " + param4
+ " param5: " + param5
+ " param6: " + param6
+ " param7: " + param7
);

//Logging statement 2
trace("Test called!")
trace("param1: " + param1)
trace("param2: " + param2)
trace("param3.length: " + param3.length)
trace("param4: " + param4)
trace("param5: " + param5)
trace("param6: " + param6)
trace("param7: " + param7)


//Logging statement 3
trace("Test called!" + " param1: " + param1 + " param2: " + param2 + " param3.length: " + param3.length + " param4: " + param4 + " param5: " + param5 + " param6: " + param6 + " param7: " + param7);


return param1;
}

They all work. But I'll tell you why I don't like the newline as a code-line separator. Because it's ambiguous. In the case above, for "logging statement 1" the new line doesn't cause the compiler to read each line as a separate action. In "logging statement 2", the new line creates separate actions.

Whereas if you use semi-colons exclusively, it becomes explicit. There is no ambiguity. You see a semi-colon, you know it's the end of that particular action. It doesn't matter where it is. And you can see why we would want to split up a logging action like that when you compare it to "logging statement 3".


If it were up to me, I'd lobby Adobe to ditch any and all leniency in their compiler. Though I do understand why they keep it accessible. As troublesome as it is, your students should get into the habit of using semi-colons. If 90% of them are having trouble remembering semi-colons, then they definitely have a ways to go -- just because it doesn't seem intuitive, doesn't mean it's ok to be a lazy programmer. And you of all people should understand that ambiguity has no place in a language. The more explicit, the better.

When I was first learning Java, I had a hard time with the semi-colon as well. But I stuck at it, and now it's second nature and I wouldn't have it any other way.

[senocular]

Bottom line. Use the semicolon.

[neves]

Thanks FizixMan, finally someone with a really good point of view :)
Here goes two solutions used by Ruby that clearly show how semicolon is really useless.



// just terminate your line with an operator, this makes clearly that the statement is not ended
trace("Test called!" +
" param1: " + param1 +
" param2: " + param2 +
" param3.length: " + param3.length +
" param4: " + param4 +
" param5: " + param5 +
" param6: " + param6 +
" param7: " + param7
)
But if you really want to start your line with plus operador, do that:



// just terminate your line with back slash,
//to say that the command is not done yet.
//Just the opposite meanning of semicolon for the rest of code
// here, I use pipe because the backslash doesn't show up
trace("Test called!" |
+ " param1: " + param1 |
+ " param2: " + param2 |
+ " param3.length: " + param3.length |
+ " param4: " + param4 |
+ " param5: " + param5 |
+ " param6: " + param6 |
+ " param7: " + param7
Do you find it ugly? Weird? Change it for a semicolon and you will know what I mean.

Since the above code, usually represents 10% of a program, you use special chars only for that sittuations. But semicolon is used just the opposite. 90% of code, you use it at the end of line, to show that the command has finished (even if the end of line has already said it).

The true is that there are languages that don't use semicolons, and are so verbose and easy to read as the others.

Have you seen that you ident your code, to make clearly that it was not finished? Python uses identation too as a scope delimiter :)

I think this thread is over now :) But if you like a good "round table" like me, use my email: marcos.neves at gmail

[FizixMan]

Identation as a scope delimiter? *shudders*

I'm sticking to my guns in that whitespace is too ambiguous to be used as a syntax construct. And in terms of Actionscript, I think Senocular said it best.