Proposal: iota, an Auto-Incrementing Counter for comptime Struct Members Summary Add iota as a built-in compile-time Int for struct comptime declarations. Inside a constructor expression T(...), iota evaluates to the previous member’s inner value plus 1 (starting at 0). An explicit literal resets th…

An enum describes an algebraic data type with a payload, whereas my proposal is aimed at representing a finite set of values within an integer range. The distinction matters because using Int as storage gives you full control over the layout, whereas with enum, the compiler has full control over the…

Yup. Sadly, the current enum proposal doesn’t do much at all if you’re interested in closed sets of values, as the OP seems to be here.

I see a lot of scepticism here. Let me explain: First of all, iota is a feature borrowed from the go programming language This it inlines with mojo’s goal of only implementing proven features. Second, the main distinction between iota with an EnumLike struct an an enum is between who owns the spar…

Proposal: `iota`, an Auto-Incrementing Counter for `comptime` Struct Members

Mojo Language Design

melodyogonna (Melody Daniel) September 26, 2026, 9:45am 2

Enum is being worked on: Pattern matching + Enum proposals

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Idea: comptime var Language Design	3	151	February 3, 2026
Mojo change: renaming `alias` to `comptime` Mojo	44	1494	November 14, 2025
Discussion: a comptime-signed int for indexing Mojo discussion	12	436	December 8, 2025
Pattern matching + Enum proposals Language Design discussion	56	1300	October 17, 2026
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Proposal: `iota`, an Auto-Incrementing Counter for `comptime` Struct Members

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