Why are tabs illegal?

[JanCVanB]

I'm personally ambivalent on tabs vs. spaces for indentation, but I'm surprised that Roc takes such a strong stance against tabs. It seems that tabs are illegal anywhere except string literals and application names:

• When used for indentation, the type checking step of the compiler throws an unformatted index out of bounds: the len is 11 but the index is 11 panic.
• When used anywhere else (such as between function arguments), the type checking step of the compiler throws a well-formatted Tab characters are not allowed. error.

Is this an intentional choice (to enforce consistency between developers? to enable the editor to use the tab key for features?) or is tab support on the roadmap?

[dullbananas]

Probably intentional. Roc is influenced by Elm, which is designed to make it easy to get started with a codebase that is new to you. It's why they banned custom infix operators, and maybe it's a reason to ban tabs.

Also, spaces are required by some disgusting code styles.

I think that Roc should require 4-space indentation because it's the default in many text editors. Roc should make it easy to get started without changing settings. For custom visual tab width, you will be able to use the Roc editor.

[rvcas]

https://github.com/ziglang/zig/issues/544

[JanCVanB]

ziglang/zig#544

Is the Roc team's approach to tabs identical to the Zig team's approach? It sounds like the Zig team plans to support tabs but doesn't at the moment. The accessibility advantages of tabs mentioned in that thread are very compelling, I've never considered them before.

[rvcas]

I just linked it because it was a very lengthy discussion with some cool information.

[JanCVanB]

I agree, very useful stuff!

[booniepepper]

The un-answerable question is: How many spaces is a tab?

(Your editor says 4, my editor says 2, a browser says 8)

I think there are some sane ways to solve it:

1. A single source file must either use only spaces or use only tabs
   • Only an indentation rule. This would mean a source file could match ^\t+ or ^ + but never both.
2. Only spaces
   • A formatter can expand tabs (maybe with a flag)
   • The editor can translate a press of the tab key to spaces
   • Any future IDE plugins do the same in a .roc file