Create the Dangling-Else Conflict, Then Fix It Three Ways

The point

Create the dangling-else conflict deliberately, read the parser's own report on it, then fix it three different ways and watch one of them break.

Do this

1. Add the two if rules with no precedence declarations. Build with bison -d -v parser.y and read the warning.
2. Open parser.output and find the conflicted state. It lists the items — productions with a dot — exactly as in the lecture notes. Copy it into your notes and identify which item wanted to shift and which wanted to reduce, and on what lookahead.
3. Test which way bison resolved it. Compile and run

   int main() {
       int x; int y;
       x = 1; y = 0;
       if (x > 0) if (y > 0) print(1); else print(2);
       return 0;
   }

   It prints 2 if the else bound to the inner if, and nothing at all if it bound to the outer one. Which happened?
4. Fix it properly with the two %nonassoc declarations. Rebuild — the warning should be gone and the behavior unchanged.
5. Swap the two declarations. Predict what the test prints now, then run it. Explain the result in terms of positional precedence.
6. Fix it a third way, on paper. Write the matched/unmatched grammar from Dragon §4.3.2 for our language. Count how many rules mentioning stmt you had to touch, and say whether you would ship it.