Error Handling

Graceful Error Handling

A robust interpreter should report errors clearly instead of crashing. We need to handle:

Types of Errors

Implementation Strategy

Instead of returning undefined or crashing, we'll throw descriptive errors and catch them at the top level:

if (node.type === "Identifier") {
    if (!(node.name in env)) {
        throw new Error("undefined variable '" + node.name + "'");
    }
    return env[node.name];
}

For division by zero:

if (node.op === "/") {
    if (r === 0) throw new Error("division by zero");
    return l / r;
}

Catching Errors

Wrap the top-level interpret call:

function interpret(input) {
    try {
        // tokenize, parse, evaluate
    } catch (e) {
        console.log(e.message);
    }
}

Your Task

Add error handling for undefined variables, division by zero, and undefined function calls. The interpreter should print the error message and continue to the next program.