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