Language Parser

CPSC 323 Group Project

    Made by @dguido1, @TimothyBui, @imjoshy & @BradK14

    at California State University Fullerton

    Fall 19'

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Table of contents

• Language Parser
  • What it does
  • Instructions
  • Starter Program
  • Steps

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What it does

• Inputs a text file with 'program code'
• Removes extra white space & comments
• Outputs an intermediate code translation in the form of a C++ program

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Instructions

• Have a program that

  • Reads in the text file final.txt
  • Formats it properly
  • Outputs the result to a second text file revised.txt
  • Command make strip will take final.txt and strip it of whitespace and comments

• Specifies production rules using Flex/Bison

• Translates the program into a high level programming language (C++)

• Command for Flex/Bison make parse will take the new revised.txt file, parse it, and convert it into working C++ code

• Runs abc13.cpp using the C++ compiler to the correct output

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Starter Program

    Suppose that the context of the text file final.txt is

	(*  Program Name: Spring 2014
	     Final Project
	     Name: Nathan Reed
	---------------------------------------------------*)
	PROGRAM aba13;
	VAR

	   ab5,  cb  ,  be, eb: INTEGER; (* declare variables *)
	BEGIN
	   ab5   =  5    ;
	   cb  =10;
	   PRINT(‘ab5=’,    ab5);
	(* compute and print the total of a and c  *)
	   eb=  cb + ab5  ;
	   PRINT(‘eb=’   ,eb )  ;

	   be  -  2*abc5 +  eb;
	   PRINT(   be  )   ;
	END.

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Steps

1. Remove all documentation, blank lines, and extra spaces from the program

• You are going to use this program to check the grammar of each statement

• The program should look like the following

  PROGRAM aba13;
  VAR
  ab5, cb, be, eb : INTEGER;
  BEGIN
  ab5 = 5;
  cb = 10;
  PRINT(‘ab5=’, ab5);
  cb = cb + ab5;
  PRINT( cb );
  be = 2 * ab5 + eb;
  PRINT( be );
  END.

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2. Specify production rules in Flex/Bison

• Given the following CFG (some rules are in EBNF form)

<start> →PROGRAM<pname>; VAR ,<dec-list>; BEGIN <stat-list> END.
<pname>     → <id>
<id>        → <letter>{<letter>|<digit>}
<dec-list>  → <dec> : <type>
<dec>       → <id>, <dec> | <id>

<stat-list> → <stat>; | <stat>; <stat-list>
<stat>      → <print> | <assign>
<print>     → PRINT (<output>)
<output>    → [“string”,} <id>
<assign>    → <id> = <expr>

<expr>      → <term> | <expr> + <term> | <expr> - <term>
<term>      → <term> * <factor> | <term> / <factor> | <factor>
<factor>    → <id> | <number> | <( <expr> )
<number>    → <digit>{<digit>}
<type>      → INTEGER
<digit>     → 0|1|2|…|9
<letter>    → a|b|c|d|e|f

• Where PROGRAM, VAR, BEGIN, END. , INTEGER, PRINT are reserved words, and all uppercase.

• Flex/bison should print out the errors, but MANUALLY fix the errors
• Your job is to use the given grammar and determine whether the program is accepted or not
  • i.e. Whether there are or aren’t syntax errors in the program.

• Your program should produce one of the following error messages as soon as the error is detected

	PROGRAM is expected (if PROGRAM is missing or spelled wrong)
	VAR     is expected (if VAR is missing or spelled wrong)
	BEGIN   is expected (if BEGIN is missing ir spelled wrong)
	END.    is expected (if END. is missing or spelled wrong)
	UNKNOWN IDENTIFIER if variable is not defined

	;       ; is missing
	‘       ‘ is missing
	.       . is missing
	(       ( is missing
	)       ) is missing
	,       , is missing
	=       = is missing

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3. If there are no errors in the program, translate the program into a C++/or another high level programming language

• Store the C++ program as abc13.cpp
  
  

• Your C++ program should look like this

#include <iostream>
Using namespace std;
int main()
{
int ab5, cb, be, eb;
ab5 = 5
cout << ”ab5=” << ab5;
eb = cb + ab5;
cout << eb;
be = 2 * ab5 + eb;
cout << be;
return 0;
}

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4. If you run the abc13.cpp file using the C++ compiler, we should be able to see the correct output