gen.subsequence / shuffle / nonEmptyListOf / uniqueListOf #11

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opened 2026-09-13 21:24:23 +09:00 by natsukium · 1 comment

natsukium commented

2026-09-13 21:24:23 +09:00

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Missing

Small list combinators every framework ships:

gen.subsequence xs — each element kept or dropped; shrinks toward dropping (Hedgehog Gen.subsequence).
gen.shuffle xs (Hedgehog Gen.shuffle, fast-check shuffledSubarray).
gen.nonEmptyListOf g.
gen.uniqueListOf lenRange g (fast-check uniqueArray); needs the filter/discard machinery or drop-duplicates.

Why

subsequence is the building block for gen.attrsWith (#4) and for "subset of declared property names" in jsonschema2nix. The others are a few lines each and keep callers from reimplementing them with bind.

Suggested shape

subsequence = xs: map (flags: filter by flags) (vectorOf (length xs) bool) — bool shrinks true -> false, so the list shrinks toward [ ].

## Missing Small list combinators every framework ships: - `gen.subsequence xs` — each element kept or dropped; shrinks toward dropping (Hedgehog `Gen.subsequence`). - `gen.shuffle xs` (Hedgehog `Gen.shuffle`, fast-check `shuffledSubarray`). - `gen.nonEmptyListOf g`. - `gen.uniqueListOf lenRange g` (fast-check `uniqueArray`); needs the filter/discard machinery or drop-duplicates. ## Why `subsequence` is the building block for `gen.attrsWith` (#4) and for "subset of declared property names" in jsonschema2nix. The others are a few lines each and keep callers from reimplementing them with `bind`. ## Suggested shape `subsequence = xs: map (flags: filter by flags) (vectorOf (length xs) bool)` — `bool` shrinks `true -> false`, so the list shrinks toward `[ ]`.

natsukium referenced this issue

2026-09-13 21:24:52 +09:00

gen.attrsOf: attrsets with generated keys #4

natsukium commented

2026-09-14 00:44:14 +09:00

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Implemented in 60d0c55, pushed to main.

Implemented in 60d0c55, pushed to main.

natsukium closed this issue

2026-09-14 00:44:14 +09:00