CS321 Prog Lang & Compilers                  Assignment # 8
Assigned: Feb. 14, 2007           Due: Monday. Feb 19, 2007


In the grammars below, all symbols that start with an
upper case letter are Non-terminals, and all other
symbols are terminals. The symbol [empty] represents
the empty string.

1) Remove the left recursion from the grammar below.

Subject    ::= Article Nounphrase
Article    ::= the  |  a
NounPhrase ::= Adjective Noun
Adjective  ::= Adjective pretty
             | Adjective red
             | [empty]
Noun       ::= ball  | cat



2) The grammar below is both ambiguous and left recursive.
It is ambiguous because the string  "x :: [y] ++ [z]" has at
least two parses. Refactor the grammar using levels, where
(x :: [y]) ++ [z] has precedence over x :: ([y] ++ [z]) and
also remove the left recursion.

List  ::= [ Item Items ]
        | [ ]
        | Item :: List
        | List ++ List
Items ::= Items , Item
        | [empty]
Item  ::= id