Assignment 3 Solution

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  • LL(1) Grammar and Recursive Descent Pars-ing

<program> ::= def <funcname> <arguments> : nn <block> EOF <funcname> ::= f j g

<arguments> ::= ( <variable> <morevars> ) <morevars> ::= , <variable> <morevars> j <block> ::= <stmtlist>

<stmtlist> ::= nt <stmt> <morestmts>

<morestmts> ::= nn <stmtlist> j

<stmt> ::= <assign> j <ifstmt> j <returnstmt>

<assign> ::= <variable> = <expr>

<condition> ::= <variable> <= <expr>

<ifstmt> ::= if <condition> : <assign> nn nt else : <assign> <returnstmt> ::= return <variable> <expr> ::= <term> + <term>

<term> ::= <variable> j <digit>

<variable> :: = a j b j c

<digit> :: = 0 j 1 j 2

nn represents the \new line” terminal. nt represents the \tab” terminal.

  1. Show that the grammar above is LL(1). Use a formal argument based on the de nition of the LL(1) grammar.

  1. Show the LL(1) parse table.

1

  1. Write a recursive descent parser for the above grammar in pseudo code in the same format as that in lecture 6.

2


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