Comment by io_eric

Reactive DOM updates – When you change state, the compiler tracks dependencies and generates efficient update code. In WebCC C++, you manually manage every DOM operation and call flush().

JSX-like view syntax – Embedding HTML with expressions, conditionals (<if>), and loops (<for>) requires parser support. Doing this with C++ macros would be unmaintainable.

Scoped CSS – The compiler rewrites selectors and injects scope attributes automatically. In WebCC, you write all styling imperatively in C++.

Component lifecycle – init{}, mount{}, tick{}, view{} blocks integrate with the reactive system. WebCC requires manual event loop setup and state management.

Efficient array rendering – Array loops track elements by key, so adding/removing/reordering items only updates the affected DOM nodes. The compiler generates the diffing and patching logic automatically.

Fine-grained reactivity – The compiler analyzes which DOM nodes depend on which state variables, generating minimal update code that only touches affected elements.

From a DX perspective: Coi lets you write <button onclick={increment}>{count}</button> with automatic reactivity. WebCC is a low-level toolkit – Coi is a high-level language that compiles to it, handling the reactive updates and DOM boilerplate automatically.

These features require a new language because they need compiler-level integration – reactive tracking, CSS scoping, JSX-like templates, and efficient array updates can't be retrofitted into C++ without creating an unmaintainable mess of macros and preprocessors. A component-based declarative language is fundamentally better suited for building UIs than imperative C++.