compile-time-typescript

Enjoy type-level programming with TypeScript!

Installation

$ npm install -g compile-time-typescript

Usage

$ ctts script.ts

Examples

There are several examples under examples/. For example, hello.ts:

type Main<Input extends string> = `Hello, ${Input}!\n`;
export default Main;

$ echo -n "world" | ctts hello.ts
Hello, world!

Remarkable features of TypeScript

• From TypeScript 4.1
  • Template Literal Types
  • Recursive Conditional Types
• From TypeScript 4.5
  • Tail-Recursion Elimination on Conditional Types
• From TypeScript 4.7
  • extends Constraints on infer Type Variables

How it works

When ctts script.ts is executed, compile-time-typescript creates a caller like this:

import Main from "/path/to/script";
type Input = "HERE COMES THE INPUT";
type Output = Main<Input>;

So the program must have a default export of a generic type that takes a type parameter and constructs a string literal type.

Then compile-time-typescript type-checks the caller and extracts the type information of Output.

If Output is a string literal type, its content is printed. Otherwise, an error occurs.

Where it is used

• hakatashi/esolang-box - Easy and standardized docker images for 200+ esoteric (and non-esoteric) languages.

Resources

• 型レベル TypeScript の esolang としての展望について - Qiita
• 第7回Esolang Codegolf Contest Writeup · hakatashi/esolang-battle Wiki