A complete RealWorld reference application (API and website) was implemented entirely in Lean 4 and passes the official API and browser test suites. The implementation uses Lean’s Std.Http server and lean-routing for typed routes, leanpostgres for Postgres access with sql! parameterization, lean-html for server-side rendering, datastar-lean for frontend interactivity, and libraries such as lean-json, lean-libcrypto, lean-jose, lean-middleware and lean-markdown. Handlers call a shared service layer, SQL rows map to Lean structures, and Datastar sends small client-side requests so no frontend build step is needed. The Lean backend is compact (≈1,033 lines), shorter than comparable TypeScript, Go and C# versions, and the codebase and libraries are on GitHub.
The writeup evaluates production readiness and correctness-by-construction. Performance currently tops out at a few thousand requests/sec/process due to a runtime bug pending release; ecosystem churn and many small contributors mean real-world hardening is needed. Full correctness-by-construction wasn’t achieved because the OpenAPI spec and tests are formal about shapes but informal about behavior, so the app was written then tested rather than derived from a formal spec. The author did prove and rely on several properties the typechecker enforces (for example, route/handler type mismatches fail at compile time) and recommends pinning the toolchain and carefully auditing handlers, SQL and C bindings before serving real users.
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Brutal, a C# framework used by RocketWerkz and other studios to develop games like RimWorld's new engine, has released its source code. The framework enables developers to build games more independently without starting from scratch, supporting multiple ongoing projects. (gamingonlinux.com)
C++26 introduces a standardized debugging header with three functions: breakpoint(), is_debugger_present(), and breakpoint_if_debugging(). These functions simplify debugger interactions by providing platform-independent ways to trigger breakpoints and detect debugger presence. (sandordargo.com)
Abner Coimbre discusses modern C conventions in C23, emphasizing the use of maybe_unused to handle unused return values and improve code clarity. He also highlights issues with designated initializers not zero-initializing structs, leading to more careful struct initialization practices. (abner.page)
Anthropic developed a custom source control system called Scion to handle their rapid increase in code changes, merging over 30,000 updates daily by September 2026. The system was built to meet extreme requirements, including managing nearly 100 GB of history and supporting 25 million code checkouts per day, replacing Git in five months. (simonwillison.net)
Concurrent ML (CML) extends Go's CSP-based concurrency model by promoting communication operations as values that can be executed separately, enabling advanced composition and encapsulation. CML also addresses goroutine leaks through garbage collection, with Racket currently leading in its implementation and support. (nikhilism.com)
Binary serialization in game data involves techniques for efficiently storing fixed and variable-sized data, such as strings and arrays. Methods like using offsets for strings help maintain constant-time access and optimize performance. (blog.demofox.org)
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