# parameter

Constructs a named parameter Path AST node with optional and regex constraints.

## Signatures

```ts
export declare const parameter: (name: string, optional?: boolean, regex?: string) => PathAst.Parameter;
```

## Why

Runtime builders retain constraints for matcher registration and schema derivation.

## Ownership and lifetime

`parameter` returns a fresh plain AST node immediately and retains any supplied child nodes or arrays by reference; it acquires no external resource.