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calculator.g4
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calculator.g4
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/*
* https://github.com/arothuis/antlr4-calculator
* just remove `Power` expression
*/
grammar calculator;
LEFT_PARENTHESIS: '(';
RIGHT_PARENTHESIS: ')';
STAR: '*';
SLASH: '/';
PLUS: ' ';
MINUS: '-';
NUMBER: [0-9] ;
WHITESPACE: [ \r\n\t] -> skip;
/*
* Production Rules (non-terminal)
*
* Production rules define how the various components
* of a language's grammar can be combined to form
* valid expressions or statements.
* Non-terminals are used in the production rules
* to indicate the structure of the language's expressions or statements,
* and to specify how the tokens and other symbols can be combined.
*/
start : expression;
/*
* The order in which expressions are evaluated
* is determined by the order in which possible
* matching rules are defined.
* Here, numbers are dealt with first, then parentheses
* and so on.
*
* Multiplication and division are on the
* same precedence level, so they are grouped.
* The same goes for addition and subtraction.
*
* Labels (e.g. "# Parentheses") are added to each rule
* to provide context to which rule is being parsed.
* This can be used in a Listener or Visitor
* to allow for separate control over Listener or Visitor actions.
*
* Likewise, inner labels (e.g. "left=expression")
* can be added to child nodes of the rule.
* This makes them identifiable in a
* Listener's or Visitor's parsing of the rule,
* allowing for even more fine-grained control.
*/
expression
: NUMBER # Number
| MINUS right=expression # Negation
| LEFT_PARENTHESIS inner=expression RIGHT_PARENTHESIS # Parentheses
| left=expression operator=(STAR|SLASH) right=expression # MultiplicationOrDivision
| left=expression operator=(PLUS|MINUS) right=expression # AdditionOrSubtraction
;