batman-nair / LL-1-Parser

LL(1) Parser for any valid grammar made in C++

LL(1) Parser

An LL(1) parser made in C++ with STL libraries.

It prints out the first, follow, parse table and checks if the given input string is accepted by the given grammar.

Usage

Compile the code with g++ and run with arguments

Grammar file contains all the productions for the grammar.

• Each line contains a production for the grammar in the format LHS->RHS
• All upper case alphabets are non-terminals or variables.
• The letter e is considered as empty string or epsilon.
• Dollar sign is used as end character.
• Any other character is taken as a terminal for the grammar

Sample Usage:

g++ parser.cpp -o parser
./parser grammar1.txt ab

Output:

Grammar parsed from grammar file:
0.  S -> AB
1.  A -> a
2.  A -> e
3.  B -> b
4.  B -> e

The non terminals in the grammar are: A B S
The terminals in the grammar are: $ a b

Firsts list:
A : a e
B : b e
S : a b e

Follows list:
A : $ b
B : $
S : $

Parsing Table:
   $ a b
A  2 1 2
B  4 - 3
S  0 0 0

Input string is accepted