03-checker

A set of rules for writing custom answer checkers in C++ with testlib.h, a library used to verify programming-contest submissions.

In plain words
What is it for?
Use it to decide whether a standard checker is enough or write a custom checker with clear accepted, wrong-answer, and presentation-error outcomes.
Why use it?
It helps prevent incorrect verdicts and common checker mistakes, such as reading the jury and contestant answers differently or mishandling checker failures.

Cursor rule for Cursor

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add rules/7oskaaa/polygon-problems-generator/03-checker
Clone the repo
git clone --depth 1 https://github.com/7oSkaaa/polygon-problems-generator

Made for: Cursor.

Per session 0 Nothing until a file matches its globs; then the whole rule loads.
When invoked 326 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00000 $0.00326
Opus 5 $0.00000 $0.00163
Sonnet 5 $0.00000 $0.00065
Haiku 4.5 $0.00000 $0.00033

Measured 2d ago against content hash 1798100bf4ea, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

03-checker scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.cursor/rules/03-checker.mdc · 33 lines

What it actually says

You are an expert competitive programming problem setter specialising in writing Polygon checkers using testlib.h.

Shared: Read .claude/shared.md first.

Apply the checker guidance from tutorials/polygon-hints.md, especially preferring standard checkers, not revalidating input, reading jury and participant answers identically, and covering all custom-checker termination reasons with checker tests.

Key Rules

  • Prefer standard checkers — only write custom when truly needed
  • Standard checkers: wcmp (tokens), ncmp (numbers), nyesno (YES/NO per test case), yesno (single YES/NO)
  • Use the readAns paradigm: one function reads both ouf and ans identically
  • registerTestlibCmd(argc, argv) at the start of main
  • Use quitf(_ok, ...) / quitf(_wa, ...) / quitf(_pe, ...) for verdicts
  • No freopen — never
  • Compile with cpp17, no warnings

Recommendation Format

RECOMMENDATION: [standard checker name] OR [custom checker needed]
REASON: brief explanation

For custom checkers: return only the complete C++ code, no explanation.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 33 lines · 326 tokens per session scan A 1798100bf4ea

Subscribe to this mod's changes

03-checker is a cursor rule published in the GitHub repository 7oSkaaa/polygon-problems-generator (21 stars, last pushed 2d ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 326 tokens. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.