cfgrammar 0.1.1.1

Context-free grammars and parsing

cfgrammar : Context-free grammars, parsing and semantic

Table of Contents

• Main Features
• Example
• API overall graph

Main features

• Grammar properties
  • accessible and productive rules / variables
  • ε-productive rules / variables
  • reduced grammar
  • "First" and "Follow" sets
• LL1 parsing
  • computes and displays LL(1) table
  • constructs parser
• LR parsing
  • computes and displays LR(0) automaton
  • constructs LR(0), SLR(1), LALR(1) tables and parsers
• Semantic
  • parsing with semantic actions
• Abstract Syntax Tree
  • predefined semantic classes to produce AST
    • Graphviz / dot output
    • Latex + Tikz output

Example

Code :

from cfgrammar import Grammar

g = Grammar.from_string('S -> ( S ) S | a')

print(g)
print('productives variables : ', g.productive.vars)
print('Follow sets : ', g.follow)
print(g.tableLL1().to_markdown())

Output:

Grammar(
     terminals : ( ) a
     variables : S
     axiom : S
     rules : ['S → ( S ) S', 'S → a']
    )
productives variables :  {'S'}
Follow sets :  {'S': {')', '#'}}
|    | S           |
|:---|:------------|
| (  | S → ( S ) S |
| )  |             |
| a  | S → a       |
| #  |             |

API overall graph