| − | Context-free grammars (or an equivalent definition using Backus-Naur-Form) are widely used both to define the syntax of programming languages and to (semi-automatically) generate parsers for these languages. | + | Context-free grammars (or equivalent definitions using Backus-Naur-Form) are widely used both to define the syntax of programming languages and to (semi-automatically) generate parsers for these languages. |