Anonymous records via named tuples.

Declare and access tuple fields with labels. An approach to anonymous records.

labels

Declare and access tuple fields with labels

This package is experimental, exploring the design space opened up by the implemented and to-be-implemented work on extensible records in GHC.

Note: You need GHC 8.0.1.

Basic examples

The haddock docs are here.

Enable these extensions:

• In GHCi: :set -XOverloadedLabels -XTypeOperators -XDataKinds -XFlexibleContexts

• In a module: {-# LANGUAGE OverloadedLabels, TypeOperators, DataKinds, FlexibleContexts #-}

Let's use GHCi:

> import Labels
> :set -XOverloadedLabels -XTypeOperators -XDataKinds -XFlexibleContexts

> (#foo := "hi", #bar := 123)
(#foo := "hi",#bar := 123)

> get #bar (#foo := "hi", #bar := 123)
123

> set #bar 66 (#foo := "hi", #bar := 123)
(#foo := "hi",#bar := 66)

> modify #mu (*0.1) (#bar := "hi", #mu := 123)
(#bar := "hi",#mu := 12.3)

> cons (#mu := [1,2,3]) (#foo := "hi", #bar := 123)
(#mu := [1,2,3],#foo := "hi",#bar := 123)

> let double field record = set field (get field record * 2) record
> double #mu (#bar := "hi", #mu := 123)
(#bar := "hi",#mu := 246)