poc(int): generic range via a Step trait - #3469
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Demonstrates that one `range(start, end, step)` can cover multiple numeric types through a minimal `Step` trait (`step_add` / `step_lt`), removing the need for per-type `Int::until` / `Int64::until` / etc. Not a production API — just a feasibility check to open design discussion. Lives as a whitebox test in `int/` for easy iteration; real home would likely be a dedicated `range` package. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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April 24, 2026 10:34
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Introduces a new `@range` package with a `Step` trait (`Add + Compare + Default`, plus a static `one()` for the default step) and a single generic `range(start, end, step?, inclusive?) -> Iter[T]` function. One entry point replaces the per-type `Int::until` / `Int64::until` / `Double::until` forms and removes the `0.until(10)` lexer trap where `0.` tokenizes as a `Double` literal. Built-in `Step` impls for `Int`, `Int64`, `UInt`, `UInt64`, `Float`, `Double`. User types opt in by implementing `Step`. Semantics mirror `Int::until` exactly — zero-step yields an empty iterator, negative step descends, inclusive=true includes `end`, and overflow near the type's max is handled the same way. Existing `::until` functions are untouched; deprecation is a follow-up. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Summary
range(start, end, step)that works across numeric types via a minimalSteptrait (step_add/step_lt).fn[T : Step] ...) are enough — we don't need "generics on traits" to unifyInt::until/Int64::until/Double::untilinto one entry point.range(0, 10, 3)is shorter than(0).until(10, step=3)and avoids the0.lexer trap where a bare integer literal followed by.methodis parsed as aDoubleliteral.What's here
int/range_test.mbt(whitebox test):trait Step, impls forIntandInt64, andfn[T : Step] range(...) -> Iter[T], plus tests.int/only so the POC compiles against existing infra; a real home would be a dedicatedrangepackage.Open design questions (for discussion)
step_add+step_lt. To matchInt::untilfully we need negative step andinclusive=true. Options: addstep_gt(or a singlestep_compare -> Int), or keep direction-specific methods.@range.range(0, 10, 3)vs@int.range(...) / @double.range(...)vs prelude export.Int::until/Int64::until/Double::untilonce the generic form lands, or keep them as thin shortcuts?Range[T]struct (not justIter[T]), we can getcontains,length,reverse, slice-indexing — at the cost of a new type in the surface area.Test plan
moon test -p intpasses locally (5256/5256).Double/UInt/Int64/ etc.🤖 Generated with Claude Code