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