lex & yacc question

["William F. Dowling" <william.dowling@isinet.com>]

Your pseudo-code has this:

/* Here I would like to create a node
				of the tree and link it with the two
				(supposed) nodes represented by each
				of the "formula"'s . 
				e.g.(in a pseudo-code):
				   new_node.symbol="&";
				   new_node.left=$1;
				   new_node.right=$3;*/

which is approximately correct.  But your c code doesn't do that:


formula: formula '&' formula { node leaf; /* only for testing: */
		     	       strcpy(leaf.symbol,"&");
		     	       leaf.left=$1;
		               leaf.right=$3;

You need to malloc() a new node and make sure it gets passed out
through $$.  Your code is only updating the lexically scoped leaf,
which disappears at the close of the block.



-- 
William F. Dowling
Institute for Scientific Information
215-386-0100 x-1156