You have to think about EBNF and ABNF as extensions that help you just to be more concise and expressive while developing your grammars. For example think about an optional non-terminal symbol, in a BNF grammar you would define it by using intermediate symbols like: A ::= OPTIONAL OTHER OPTIONAL ::= opt_part | epsilon while … Read more
The YACC syntax is in the Ruby source. Download it and run the bundled utiliy to get the readable syntax. wget ftp://ftp.ruby-lang.org/pub/ruby/2.0/ruby-2.0.0-p195.tar.gz tar xvzf ruby-2.0.0-p195.tar.gz cd ruby-2.0.0-p195 ruby sample/exyacc.rb < parse.y Output sample (total 918 lines for the v2.0.0-p195) program : top_compstmt ; top_compstmt : top_stmts opt_terms ; top_stmts : none | top_stmt | top_stmts … Read more
It’s not always easy (or even possible) to demonstrate that a grammar is ambiguous, but if there is a short ambiguous sentence, then it can be found with brute-force enumeration, which is what I believe that tool does. And the output is revealing; the shortest ambiguous sentence is the empty string. So it remains only … Read more
In the context of computer science, a word is the concatenation of symbols. The used symbols are called the alphabet. For example, some words formed out of the alphabet {0,1,2,3,4,5,6,7,8,9} would be 1, 2, 12, 543, 1000, and 002. A language is then a subset of all possible words. For example, we might want to … Read more
There is an Online Railroad Diagram Generator. It creates SVG syntax diagrams, also known as railroad diagrams, from context-free grammars specified in EBNF. You can copy the SVG code or take screen shots. You have to type in the grammar and it’ll make the diagram. For example, to create the first railroad diagram you show, … Read more