43 lines
1.2 KiB
JavaScript
43 lines
1.2 KiB
JavaScript
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export const treewalk = {};
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export const builtins = {};
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treewalk.init = (input) => {
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return { input };
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};
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treewalk.eval = (state, node) => {
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switch (node.kind) {
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case "integer":
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let sourceString = state.input.substring(node.start, node.end);
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return parseInt(sourceString);
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case "list":
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let functionToCall = node.children[0];
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let builtin = builtins[state.input.substring(functionToCall.start, functionToCall.end)];
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return builtin(state, node);
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default:
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throw new Error(`unhandled node kind: ${node.kind}`);
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}
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};
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export function run(input, node) {
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let state = treewalk.init(input);
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return treewalk.eval(state, node);
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}
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function arithmeticBuiltin(op) {
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return (state, node) => {
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let result = treewalk.eval(state, node.children[1]);
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for (let i = 2; i < node.children.length; ++i) {
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result = op(result, treewalk.eval(state, node.children[i]));
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}
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return result;
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};
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}
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builtins["+"] = arithmeticBuiltin((a, b) => a + b);
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builtins["-"] = arithmeticBuiltin((a, b) => a - b);
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builtins["*"] = arithmeticBuiltin((a, b) => a * b);
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builtins["/"] = arithmeticBuiltin((a, b) => a / b);
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