Using the command make, the project is compiled using the ghc compiler and a program simplify-bkg is created.

After the compilation (see the section above), it can be run as follows:

$ ./simplify-bkg (-i|-1|-2) [input-file]

input-file is the name of an input file. If it is not specified, the program reads the standard input. With the option -i, the program prints the loaded context-free grammar. With the option -1, the program prints the context-free grammar without nonterminal symbols that generate nonterminal strings. With the option -2, the program prints the context-free grammar without nonterminal symbols that generate nonterminal strings and without unreachable symbols.

The program removes unnecessary symbols from the context-free grammar. An input grammar is first validated and in case of invalid format or invalid grammar, an error message is printed to the standard error output and the program is terminated with an error code. Otherwise, the unnecessary symbols are removed and the grammar is printed to the standard output. The source codes are located in the following files:

• Types.hs - Definitions of data types. The internal representation of the context-free grammar.
  • The grammar is represented as a structure where nonterminal symbols are a list of characters, terminal symbols are a list of characters, the starting symbol is a character, and production rules are a list of pairs where the left side of the rule is a character and the right side is a list of characters.
• Parser.hs - An input parser. Parsing and validating an input grammar and converting it to the internal representation.
  • The library Text.Parsec is used for parsing the input grammar.
• Simplification.hs - An implementation of the simplification of the context-free grammar algorithm.
• Main.hs - The main program. Performs input and output operations. Initiates the computation.