Claude Opus 5.5 (effort default (no --effort flag) · thinking on) on Write a lexer, parser and evaluator for a small closure-based language from a 1-page spec

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  "result": "The Tiny interpreter is written in `tiny.py`. It has a lexer, a recursive-descent parser and a tree-walking evaluator, uses only the standard library, and both `run(source)` and `TinyError` are in place.\n\n**Testing:** I ran about 30 small programs of my own and all gave the expected output or error. They covered arithmetic, comparisons, strings, scopes, closures and recursion, plus most of the error messages and line numbers. I haven't run the real grader. A recursion 200 calls deep works, and the 201st call fails with `line N: stack overflow` at that call's line. My first deep-recursion check reported a stack overflow, but that was my test's fault: it asked for 201 nested calls. Rerun at 199, it passed. A Fibonacci(20) program ran in under 0.1 seconds.\n\n**How deep recursion is handled:** each program runs in its own thread with a 512 MB stack and a raised Python recursion limit, so recursion up to the limit doesn't crash Python. Very large integers print in full, because I switched off Python's 4300-digit limit on converting integers to text.\n\n**Where the spec was ambiguous, I chose:**\n- **`return` outside a function** is caught when it runs, not while parsing. So a top-level `return` in a branch that never executes doesn't cause an error.\n- **Function parameters and the function body share one scope.** So `fn f(a) { let a = 1 }` fails with `already declared`.\n- **Bare `{ ... }` blocks** that aren't attached to an `if`, `while` or function are a syntax error, since the spec doesn't list them as statements.\n- **Extra detail in messages:** errors include the name where it helps (e.g. `already declared x`), and syntax errors say what was unexpected. The spec allows extra detail after the required text.\n- **Call errors** (`type error`, `arity mismatch`, `stack overflow`) report the line of the call's opening `(`.\n- **A newline inside a string** is kept as part of the string rather than treated as an error.",
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