ANTLR 4 tree inject/rewrite operator

As mentioned by Sam (280Z28), ANTLR 4 does not have rewrite operators. When generating the parser, ANTLR 4 creates some listener classes that you can use to listen for “enter” and “exit” events of all parser rules. Also, ANTLR 4 supports “direct left recursive rules”, so your expression rules can be defined in a single … Read more

When is EOF needed in ANTLR 4?

You should include an explicit EOF at the end of your entry rule any time you are trying to parse an entire input file. If you do not include the EOF, it means you are not trying to parse the entire input, and it’s acceptable to parse only a portion of the input if it … Read more

When is EOF needed in ANTLR 4?

You should include an explicit EOF at the end of your entry rule any time you are trying to parse an entire input file. If you do not include the EOF, it means you are not trying to parse the entire input, and it’s acceptable to parse only a portion of the input if it … Read more

What does “fragment” mean in ANTLR?

A fragment is somewhat akin to an inline function: It makes the grammar more readable and easier to maintain. A fragment will never be counted as a token, it only serves to simplify a grammar. Consider: NUMBER: DIGITS | OCTAL_DIGITS | HEX_DIGITS; fragment DIGITS: ‘1’..’9′ ‘0’..’9’*; fragment OCTAL_DIGITS: ‘0’ ‘0’..’7’+; fragment HEX_DIGITS: ‘0x’ (‘0’..’9′ | … Read more

What is a ‘semantic predicate’ in ANTLR?

ANTLR 4 For predicates in ANTLR 4, checkout these stackoverflow Q&A’s: Syntax of semantic predicates in Antlr4 Semantic predicates in ANTLR4? ANTLR 3 A semantic predicate is a way to enforce extra (semantic) rules upon grammar actions using plain code. There are 3 types of semantic predicates: validating semantic predicates; gated semantic predicates; disambiguating semantic … Read more