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java-lexer-parser-for-grammars

Java Lexer/Parser for Grammars

Grammar:

Expression = BooleanExpression .

BooleanExpression = BooleanTerm { "or" BooleanTerm } .

BooleanTerm = BooleanFactor { "and" BooleanFactor } .

BooleanFactor = [ "not" ] ArithmeticExpression [ ( "=" | "<") ArithmeticExpression) ] .

ArithmeticExpression = Term { ("+" | "-") Term } .

Term = Factor { ("*" | "/") Factor } .

Factor = Literal | Identifier | "(" Expression ")" .

Literal = BooleanLiteral | IntegerLiteral .

BooleanLiteral = "false" | "true" .

IntegerLiteral = Digit { Digit } .

Identifier = Letter { Letter | Digit | "_" }.

Digit = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" .

Letter = "a" | "b" | "c" | "d" | "e" | "f" | "g" | "h" | "i" | "j" | "k" | "l" | "m" | "n" | "o" | "p" | "q" | "u" | "r" | "s" | "t" | "u" | "v" | "w" | "x" | "y" | "z" | "A" | "B" | "C" | "D" | "E" | "F" | "G" | "H" | "I" | "J" | "K" | "L" | "M" | "N" | "O" | "P" | "Q" | "U" | "R" | "S" | "T" | "U" | "V" | "W" | "X" | "Y" | "Z" .

Comments:

  1. Integer literals and identifiers are treated as complete terminal symbols. That is, id is a single terminal symbol, not a sequence of two symbols (i and d).

  2. White space is allowed anywhere, except within terminal symbols.

  3. A comment begins with a double slash (//) and terminates at the end of line.

  4. "Maximum munch" applies. For example, begin1 is an identifier, unlike begin 1, which is the keyword begin followed by the integer 1.

  5. Do not attach too much importance to the names of the various kinds of expression: they do not always indicate the type.