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pegjs/examples/arithmetics.pegjs

23 lines
530 B
JavaScript

/*
* Classic example grammar, which recognizes simple arithmetic expressions like
* "2*(3+4)". The parser generated from this grammar then computes their value.
*/
start
= additive
additive
= left:multiplicative "+" right:additive { return left + right; }
/ multiplicative
multiplicative
= left:primary "*" right:multiplicative { return left * right; }
/ primary
primary
= integer
/ "(" additive:additive ")" { return additive; }
integer "integer"
= digits:[0-9]+ { return parseInt(digits.join(""), 10); }