[antlr-interest] Re: matching an AST segment with Java 5
John Green
greenj at ix.netcom.com
Wed Jul 26 09:59:04 PDT 2006
Whoops, that's really incomplete. I hit send too soon. How embarrassing. Need more coffee. Please delete my last post and pretend you didn't see it. :-/
John Green wrote:
> John Green wrote:
>> // Looking for: #(PLUS #(PLUS NUMBER NUMBER) NUMBER)
>> // and if found, print the text of the first NUMBER node.
>> Object [] match = match(currentNode,
>> new Object[]{PLUS, new Object[]{PLUS, NUMBER, NUMBER}, NUMBER}
>> );
>
>
> Filling in the code for match() was easy. Here's a quick test mTest(),
> which calls a sample usage m(), which calls match().
>
>
> private static final int PLUS = 20;
> private static final int NUMBER = 30;
> void mTest() {
> AST p1 = new CommonAST(); p1.setType(PLUS);
> AST p2 = new CommonAST(); p2.setType(PLUS);
> AST n1 = new CommonAST(); n1.setType(NUMBER); n1.setText("1");
> AST n2 = new CommonAST(); n2.setType(NUMBER); n2.setText("2");
> AST n3 = new CommonAST(); n3.setType(NUMBER); n3.setText("3");
> p1.setFirstChild(p2);
> p2.setFirstChild(n1);
> n1.setNextSibling(n2);
> p2.setNextSibling(n3);
> m(p1);
> }
>
> void m(AST currentNode) {
> // Looking for: #(PLUS #(PLUS NUMBER NUMBER) NUMBER)
> // and if found, print the text of the first NUMBER node.
> Object [] match = match(
> currentNode
> , new Object[]{PLUS, new Object[]{PLUS, NUMBER, NUMBER},
> NUMBER}
> );
> if (match!=null) {
> System.out.println(((AST)((Object[])match[1])[1]).getText());
> } else {
> System.out.println("No match");
> }
> }
>
> Object[] match(AST ast, Object[] objarray) {
> if (ast==null) return null;
> Object[] ret = new Object[objarray.length];
> ret[0] = ast;
> AST currAST = ast.getFirstChild();
> for (int count = 1; count < objarray.length; count++) {
> if (currAST==null) return null;
> if (objarray[count] instanceof Object[]) {
> Object[] nonterminal = match(currAST,
> (Object[])objarray[count]);
> if (nonterminal==null) return null;
> ret[count] = nonterminal;
> } else {
> ret[count] = currAST;
> }
> currAST = currAST.getNextSibling();
> }
> return ret;
> }
>
>
>
>
>
> John Green wrote:
>> With Java 5 and autoboxing, I could use nested Object arrays as a
>> quick and dirty description for a segment of an AST. Has anybody done
>> this sort of thing before? Specifically, I wonder if match(AST,
>> Object[]) as per my "usage example" below has been written and exists
>> in any of the Antlr or other libraries.
>>
>> It'll be easy to write, I'd just rather use existing libraries. :)
>> <snip>
>>
>> Cheers,
>> John
>> www.joanju.com
>>
>
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