# Lecture 06

## Exercise 1

Given the following grammar:

S → AaB | aBb A → a | C B → FAb | bA C → CDB | ϵ D → A | B | ab E → b | A F → aF

- Remove ϵ-productions, unit productions and useless non-terminals.
- Put the resulting grammar into Chomsky Normal Form.
- Argue if it is possible to apply the modifications in the first part in different orders.

## Exercise 2

A CYK parser is parsing the input “Int , Int ⇒ Int”. The incomplete tables for two different grammars are given below.

- Complete the table.
- Find the suitable grammar that actually generates the table.
- Construct the table for “Int , Int ⇒ Int , Int”.

## Exercise 3

Consider a context-free grammar without unit or ε-productions. Assume that the maximum number of symbols on the right hand side of any production is . Show that there exists an equivalent grammar in Chomsky normal form with no more than production rules. The set is the set of production rules and is the set of terminals.