Parsing a MOOL program

A first step is probably to write a flex/lex program and yacc program in order to obtain a parser for a MOOL program. The only goal of this parser is to check whether an input text file is a valid MOOL program or not, that is a program which can be generated by the above grammar.

• So the flex/lex program and the yacc program implements the grammar of MOOL described above.
• And the actions of the yacc program are limited to message printing.

Since the grammar of a true programming language like MOOL is more complicated than the little examples of a lecture, one should divide this task into subtasks.

• First one could write a parser for the top level of the grammar only. To do so one can add the following dummy rules.

  ArithmeticExpression	$\longmapsto$	1
  Body	$\longmapsto$	id

• Second for the middle level (bodies) by adding dummy rule like

  BooleanExpression

  $\longmapsto$

  true

• Lastly for the low level (arithmetic and boolean expressions).