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