Hi folks,
I am still struggling with the semantic analysis in my little
compiler. First of all here is what I have so far.
* On the parser level I allow operators to be used on all kinds
operands e.g:
"true + false " would be accepted by my parser an converted to ^(+
true false)
* To still catch such errors I introduced an extra compiler stage in
the form of a TreeWalker containing rules like the following:
expression returns [String returntype]
:
^(PLUS a=expression b=expression)
{
if($a.returntype.equals("int")&& $b.returntype.equals("int"))
{
$returntype="int";
}
else if ($a.returntype.equals("int")&& $b.returntype.equals("float"))
{
//TODO convert all ints in the left subtree to float
$returntype="float";
}
else if ($a.returntype.equals("float")&& $b.returntype.equals("int"))
{
//TODO convert all ints in the right subtree to float
$returntype="float";
}
else if ($a.returntype.equals("float")&&
$b.returntype.equals("float"))
{
$returntype="float";
}else
{
throw new InvalidTypeException();
}
}
-> ^(PLUS $a $b)
Unfortunately I still have two problems with this:
1. How can I throw a detailed Error Message saying something like "The
operator + is invald for the types of "+ $a.returntype + " and "+
$b.returntype
2. How can I modifiy the tree returned by $a so that I can replace
every token like INT:3 with a token of FLOAT:3.0. So that (+ 3 4.0)
becomes (+ 3.0 4.0)
I would write a recursive method for doint the tree manipulation but
my main problem is, that I do not know how to "reattach" the modfied
subtree to my result.
$a.tree=castIntToFloat($a.tree) won't work because $a.tree is
readonly :-(
kind regards & thanks in advance
Tilman Bender
Student des Software Engineering
Hochschule Heilbronn
[email protected]
--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"il-antlr-interest" group.
To post to this group, send email to [email protected]
To unsubscribe from this group, send email to
[email protected]
For more options, visit this group at
http://groups.google.com/group/il-antlr-interest?hl=en
-~----------~----~----~----~------~----~------~--~---
List: http://www.antlr.org/mailman/listinfo/antlr-interest
Unsubscribe:
http://www.antlr.org/mailman/options/antlr-interest/your-email-address
