LTGen

LTGen stands for Language Theory GENerator and provides tools to implement language theory.

Command Line

LTGen is a collection of tools to implement basic algorithms used in Language Theory. The command line arguments are mostly the same for the provided tools:

$ ltgen.py GRAMMAR OPTIONS

Where GRAMMAR is path to a file containing the grammar to work with (format is detailed below).

OPTIONS are detailed in the following sections but some (provided below) are shared by all tools:

• --k -- select the lookup depth used in the tools.
• --table -- output the analysis table (if any).
• --gen-csv -- output the analysis table in CSV (if any).
• --output|-o PATH? -- output to the analysis table to a file (with the given PATH or to path derived from the grammar file).
• --word|-w "WORD" -- scan the WORD with the current analysis (separate non-terminals in the word by spaces).
• --print -- print the current grammar (useful un conjunction with --word).

If no options is given, the used grammar is just displayed.

LL(k) Analysis

LTgen provides basics for LL(k) analysis:

• --first -- computes first_k(X) for all or for listed non-terminals,
• --follow -- computes follow_(k) for all or for listed non-terminals,
• --lookahead -- computes k-lookahead(X -> s) for all or for listed nion-terminal productions.
• --ll -- Test if the given grammar is LL(k).

.gram Files

Grammar can be expressed using .gramfiles. The format is very simple:

• Rules are organized by lines.
• A rule has the format: NAME -> SYM1 SYM2 ...
• A symbol or a rule name can be any sequence of character that do contain spaces or tabulations.
• The name of the first rule is the axiom of the grammar.
• Empty lines are accepted.
• Comments spans from the # to the end of the line.
• Notice that the symbol $ is reserved to mark the end of word.

Example of grammar:

S'	->	S
S	->	a S b
S	->	R
R	->	b
R	->	c R

Testing

Unit is performed using pytest with the command:

$ pytest test.py