Meaning of => in EBNF notation -

in ebnf notation see many => cannot find description. googled , read pdf , wikipedia, still no clue.

assignmentexpression:     (lefthandsideexpression assignmentoperator) =>     lefthandsideexpression assignmentoperator assignmentexpression     | conditionalexpression     ; 

my guess is, it's hint or directive parser (probably recursive-descent). e.g., if you're trying parse assignmentexpression, , can parse prefix of pending input lefthandsideexpression assignmentoperator, commit parsing lefthandsideexpression assignmentoperator assignmentexpression alternative of assignmentexpression.