vinyl-loeb: Loeb's theorem for extensible records.

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Dependencies base (>=4.7 && <5), vinyl [details]
License MIT
Copyright 2020 Daniel Firth
Author Daniel Firth
Category Vinyl
Source repo head: git clone
Uploaded by locallycompact at 2020-12-07T02:24:01Z
Distributions LTSHaskell:, NixOS:, Stackage:
Downloads 240 total (14 in the last 30 days)
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Status Docs available [build log]
Last success reported on 2020-12-07 [all 1 reports]

Readme for vinyl-loeb-

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This package defines a version of loeb's theorem for vinyl.

rloeb :: RMap xs => Rec ((->) (Rec f xs) :. f) xs  -> Rec f xs
rloeb x = go where go = rmap (($ go) . getCompose) x

This can be used to fill up an extensible record lazily using data from the result of the record itself.

type F = [Text, Text]

k :: Rec Thunk F -> Text
k (Thunk f :& _) = f <> "bar"

f :: Rec ((->) (Rec Thunk F) :. Thunk) F
f = (Compose $ const $ Thunk $ "foo") :& Compose (Thunk . k) :& RNil

-- > rloeb f
-- {"foo", "foobar"}