BangScript is a gradually-typed compiled programming language. It features Runtime Bounded Typing (RBT), a novel approach to type safety that bridges static and dynamic typing through explicit, atomic runtime type assertions.
BangScript is designed for developers who want the safety of static types without the ceremony of traditional type systems. It draws syntax from Lua, TypeScript, and C, but reimagines how type checking works at runtime.
The language is expression-oriented: if, match, for, and while all return values. Functions are declared with fn for named procedures and ld for lambdas. Variables use let for mutability and const for immutability. Type annotations use the :: postfix operator.
RBT is BangScript's core type system feature. It provides three operators for runtime type assertions:
| Operator | Behavior | Returns |
|---|---|---|
!T expr |
Prove: checks type at runtime, fatal error if wrong | T |
!~T expr |
Mask: checks type at runtime, returns nil if wrong |
T | nil |
?T expr |
Query: checks type at runtime, returns boolean | Bool |
RBT operates on the Unknown type, which represents values whose type cannot be statically determined. This enables safe interaction with untyped data sources while maintaining explicit, searchable type contracts in code.
The compiler elides RBT checks when types are already statically proven, making them zero-cost in typed contexts.
let mixed :: List<Unknown> = [1, "Hello"]
let proved = !String mixed[1]
// proved = "Hello"
let cantProve = !Integer mixed[1]
// RBT Error: Cannot prove that "mixed[1]" is of type "Integer"
let masked = !~Integer mixed[1]
// masked = nil| Feature | Choice |
|---|---|
| Indexing | 0-based |
| Semicolons | Optional (newline terminates) |
| Tail calls | Guaranteed optimization for ld |
| Memory | GC by default, unsafe blocks for C interop |
| Object orientation | None — structs and functions only |
BangScript is in early development.
MIT