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31 lines
781 B
JavaScript
31 lines
781 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[0] === "+") return result + element[1];
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if (element[0] === "-") return result - element[1];
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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[0] === "*") return result * element[1];
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if (element[0] === "/") return result / element[1];
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}, head);
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}
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Factor
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= "(" _ @Expression _ ")"
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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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