- Terminals: Stuff on right hand side not in left hand side (eg. id num + % /…)
- non-terminals: All unique elements on left hand side (eg. Expr… Term Tail)
Steps to draw a parse tree
- Id all terminals
- Use non-terminals to build struct following rules based on expr (go step by step based on the rules)
- ANY non-terminals have no child.
- The () operator should have 3 lines
( expr )one for each
Ambiguous?
- Grammar produces at least 2 distinct parse tree/derivations→ ambiguous!
- same non-terminal appears twice on a right hand side of the production then it has the ambiguity problem
Productions
Find out how many productions in the given grammer:
- How many outputs are in a given grammer? eg. below: has 10 outputs = productions (how many expressions are outside the divided by
\which is a OR) - In this case just 10 expr by this fact