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// Simple Arithmetics Grammar
// ==========================
//
// Accepts expressions like "2 * (3 + 4)" and computes their value.
Expression
= head:Term tail:(_ @("+" / "-") _ @Term)* {
return tail.reduce(function(result, element) {
if (element[0] === "+") return result + element[1];
if (element[0] === "-") return result - element[1];
}, head);
}
Term
= head:Factor tail:(_ @("*" / "/") _ @Factor)* {
return tail.reduce(function(result, element) {
if (element[0] === "*") return result * element[1];
if (element[0] === "/") return result / element[1];
}, head);
}
Factor
= "(" _ @Expression _ ")"
/ Integer
Integer "integer"
= _ [0-9]+ { return parseInt(text(), 10); }
_ "whitespace"
= [ \t\n\r]*