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Topic: little dumb question (Read 275 times) |
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lunetta
 
 
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little dumb question
« on: Apr 25th, 2004, 8:24pm » |
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int a = 1;
void setup() {
a = 2;
a = 3;
}
a = 4;
void loop() {
a = 5;
println (a);
}
this simple example does not work;
why can't I reassign a global variable outside the voids? It's not a truly necessary thing, I was just wondering the reason...
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fry
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Re: little dumb question
« Reply #1 on: Apr 25th, 2004, 11:23pm » |
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because there's no determination for when the 'a=4' line would be run. is it when the program is first created? is it before setup()?
java, and therefore processing, programs are built around methods (like setup/loop/etc) so everything must be inside a method.
the difference is that in 'static' mode, where there are no methods at all, processing cheats and puts your entire program inside 'setup' behind the scenes. so this program:
int a = 1;
println(a);
becomes:
void setup() {
int a = 1;
println(a);
}
when you hit the 'run' button.
on the other hand, the difference with the 'int a = 1' at the beginning, is that this has a specific timing--that when the program is first created, a slot for something called 'a' will be created, and it will initially be filled with '1'.
that make sense?
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mflux
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Re: little dumb question
« Reply #2 on: Apr 26th, 2004, 12:02am » |
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Hi Ben
That makes sense, but what about declaring and initializing an instance of an object?
Ball a=new Ball();
class Ball
{
Ball()
{
}
}
void setup()
{
}
void loop()
{
}
This would not work, even though it's much like making a new variable and intializing it. I'm forced to do:
Ball a;
class Ball
{
Ball()
{
}
}
void setup()
{
a=new Ball();
}
void loop()
{
}
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| « Last Edit: Apr 26th, 2004, 12:03am by mflux » |
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fry
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Re: little dumb question
« Reply #3 on: Apr 26th, 2004, 5:14am » |
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that first program runs just fine for me, as it should.
if you're getting a problem with that type of thing, it's more likely to be in the preprocessor or compiler (and a bug), because as you point out, it should work.
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lunetta
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Re: little dumb question
« Reply #4 on: Apr 26th, 2004, 5:42am » |
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thanks guys for the attention;
this wasn't a problem I'm experiencing, but something I wanted to understand. It's clear now, thanks!
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