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Suggestion: Shorthand Syntax for Fixed-Length Single-Type Tuple (e.g. [number: 4]) #62481
Description
🔍 Search Terms
fixed length single type tuple shorthand
✅ Viability Checklist
- This wouldn't be a breaking change in existing TypeScript/JavaScript code
- This wouldn't change the runtime behavior of existing JavaScript code
- This could be implemented without emitting different JS based on the types of the expressions
- This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, new syntax sugar for JS, etc.)
- This isn't a request to add a new utility type: https://github.com/microsoft/TypeScript/wiki/No-New-Utility-Types
- This feature would agree with the rest of our Design Goals: https://github.com/Microsoft/TypeScript/wiki/TypeScript-Design-Goals
⭐ Suggestion
Introduce a concise syntax for declaring fixed-length tuples consisting of a single repeated type. For example, instead of writing [number, number, number, number], allow [number: 4] to represent a tuple of four numbers.
📃 Motivating Example
Current syntax for fixed-length tuples requires repetition. This can be a bit awkward if the tuple has many elements:
type Matrix3x3 = [number, number, number, number, number, number, number, number, number];With the proposed shorthand:
type Matrix3x3 = [number: 9];This is especially useful for mathematical vectors, matrices, and APIs expecting tuples of a fixed size and type.
💻 Use Cases
- Declaring fixed-size vectors or matrices in math/graphics code
- APIs in other domains with similar semantical requirement
Activity
IllusionMH commentedon Sep 24, 2025
Isn't proposed syntax already used for named tuples?
Example should create length 1 tuple with element named
numberand type (literal)9.MartinJohns commentedon Sep 24, 2025
Duplicate of #47874.
hillin commentedon Sep 24, 2025
Yeah you are definitely right, I didn't pay too much attention to the syntax, it's just a placeholder. I'd be totally happy with a better syntax for the same semantics (say,
[number; 9]like rust's fixed-length array declaration).hillin commentedon Sep 24, 2025
I knew there would be an existing issue!
Unfortunately the author of that issue did not come up with a good real world example. In the maths/CG area this could be much more a real QoL improvement.
snarbles2 commentedon Sep 24, 2025
The linked issue points out this is something you can create yourself with code example included.