Tidyparse has a browser demonstration for exploring syntax, grammar rules and suggested completions. The page combines an editable grammar and test-case area with instructions for inspecting continuations and invalid snippets. Built-in examples include a toy while language, checked arithmetic, Boolean algebra, lambda calculus, definition-before-use, Python and a custom grammar in Chomsky normal form.
The demonstration updates when the editor content changes. Users can move through completions with the arrow keys and apply a selection, while a suffix mode supports accepting the next token of a continuation. Soft gray text previews a possible continuation, and the instructions explain how Tab accepts it. Nonterminal stubs appear in angle brackets and can also be replaced through the keyboard.
Invalid snippets are marked with a squiggly underline. The page distinguishes unparseable fragments from unknown terminals with different colors, helping visitors inspect why a sequence does not fit the supplied grammar. Additional controls expose a generation timeout, maximum edit distance, optional empty productions and nonterminal stubs. This is a technical demonstration for experimenting with grammar-driven completion and error feedback, rather than a general writing assistant or a claim that a suggested program has the intended runtime behavior. The quality of the interaction depends on the grammar and examples supplied.
