SimpleParser

Features

fast to setup and easy to use
can parse ebnf-grammar
- terminal strings
- groupings
- optionals
- alternations
- repetitions
- rules
- variables (not ebnf, can be any string,number or boolean)
result as detailed or minimized tree (unnecessary nodes can be removed)

Creating a grammar

// OR_EXPRESSION 	-> AND_EXPRESSION {"or" AND_EXPRESSION}
// AND_EXPRESSION 	-> COMPONENT {"and" COMPONENT}
// COMPONENT 		-> STATEMENT | ( "(" EXPRESSION ")"
// STATEMENT		-> "e"

GrammarBuilder gb = new GrammarBuilder();

// OR_EXPRESSION 	-> AND_EXPRESSION {"or" AND_EXPRESSION}
gb.defineRootNonTerminal("OR_EXPRESSION",
 gb.sequence(
  gb.nonTerminal("AND_EXPRESSION"),
  gb.zeroOrMore(
   gb.sequence(
    gb.terminal("or"),
    gb.nonTerminal("AND_EXPRESSION")
   )
  )
 )
);

// AND_EXPRESSION 	-> COMPONENT {"and" COMPONENT}
gb.defineNonTerminal("AND_EXPRESSION",
 gb.sequence(
  gb.nonTerminal("COMPONENT"),
  gb.zeroOrMore(
   gb.sequence(
    gb.terminal("and"),
    gb.nonTerminal("COMPONENT")
   )
  )
 )
);

// COMPONENT 		-> STATEMENT | ( "(" EXPRESSION ")"
gb.defineNonTerminal("COMPONENT",
 gb.alternative(
  gb.nonTerminal("STATEMENT"),
  gb.sequence(
   gb.terminal("("),
   gb.nonTerminal("OR_EXPRESSION"),
   gb.terminal(")")
  )
 )
);

// STATEMENT	-> "e"
gb.defineNonTerminal("STATEMENT", gb.terminal("e"));

// GRAMMAR
Grammar grammar = gb.get();

Parsing a String

StringParser parser = new StringParser(grammar);
ParserResult result = parser.parse(strInput, false, false);

Visualizing Grammar or ParserResult as a tree/graph

String tree = DotTreeBuilder.build(result.getRoot())
String graph = DotGrammarBuilder.build(grammar, result.getTrace());

"tree" and "graph" can be visualized for example with "Graphviz" or in the browser with http://viz-js.com/

the grammar as a graph

resuling tree of the input "e and (e or e)"

Debugging

If the input does not match the grammar, an error is returned with a partial tree that also contains error-nodes specifying what went wrong.

resuling tree of the input "e and (

While parsing an input, the parser generates a "trace". A trace records every step and its state (match,no-match,error). The output trace can be output together with the final tree as a .dot-graph.