Re: [Dltk-dev] equals() in AST nodes

[Charles Doucette <cdoucette@xxxxxxxxxxx>]

There is an issue with equals.
Consider the following statement:

int i=2;
int j=0;
switch (i) {
case 2:
	j=1;
	break;
case 2:
	j=2;
	break;
}

One of our users wanted us to do semantic checking to determine if the  
second case statement was "equal" (equivalent) to the first. If so, we  
should flag it as a duplicate. Thus, I wanted to use ASTNode.equals to  
check for the duplicate node. Unfortunately, equals fails since each  
node includes the start position within the buffer - and those aren't  
equal.

It would be useful to have a method that could be used to indicate the  
everything but position was equal. I'm not sure what such a method  
should be called.

Chuck

On Jun 10, 2009, at 9:28 AM, Michael Spector wrote:

> Hi All,
>
> Is there any reason to have equals() methods in basic AST nodes  
> implemented in DLTK core?
> I guess it ASTNode should have the following to disallow weird and  
> useless implementations of equals() in class hierarchy:
>
> 	public final boolean equals(Object obj) {
> 		return this == obj;
> 	}
>
> 	public final int hashCode() {
> 		return super.hashCode();
> 	}
>
> What do you think?
>
> Thanks,
> Michael
> <ATT00001.c>