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Example Recursive Descent Parser

By Tim Henderson

Setup

$ git clone https://github.com/cwru-compilers/recursive.git
$ cd recursive
$ virtualenv --no-site-packages env
$ . env/bin/activate
$ pip install -r requirements.txt

Run the tests

$ nosetests

Notes

  1. The Lexer is handwritten and in lexer.py
  2. There are tests which can be run with nosetests

Grammar

Original

Expr   -> Expr PLUS Term
        | Expr DASH Term
Term   -> Term STAR Unary
        | Term SLASH Unary
Unary  -> DASH Factor
        | Factor
Factor -> NUMBER
        | LPAREN Expr RPAREN

LL(1)

Expr   -> Term Expr_
Expr_  -> PLUS Term Expr_
        | DASH Term Expr_
        | e
Term   -> Unary Term_
Term_  -> STAR Unary Term_
        | SLASH Unary Term_
        | e
Unary  -> DASH Factor
        | Factor
Factor -> NUMBER
        | LPAREN Expr RPAREN