Changelog for singletons-base-3.0
Changelog for the singletons-base
project
3.0 [2021.03.12]
-
The
singletons
library has been split into three libraries:- The new
singletons
library is now a minimal library that only providesData.Singletons
,Data.Singletons.Decide
,Data.Singletons.Sigma
, andData.Singletons.ShowSing
(if compiled with GHC 8.6 or later).singletons
now supports building GHCs back to GHC 8.0, as well as GHCJS. - The
singletons-th
library defines Template Haskell functionality for promoting and singling term-level definitions, but but nothing else. This library continues to require the latest stable release of GHC. - The
singletons-base
library defines promoted and singled versions of definitions from thebase
library, including thePrelude
. This library continues to require the latest stable release of GHC.
Consult the changelogs for
singletons
andsingletons-th
for changes specific to those libraries. For more information on this split, see the relevant GitHub discussion. - The new
-
Require building with GHC 9.0.
-
The modules in
singletons-base
have been renamed to better reflect the modules frombase
from which they take inspiration. In particular, the following module renamings have been applied:Data.Singletons.CustomStar
->Data.Singletons.Base.CustomStar
Data.Singletons.Prelude
->Prelude.Singletons
Data.Singletons.Prelude.Applicative
->Control.Applicative.Singletons
Data.Singletons.Prelude.Bool
->Data.Bool.Singletons
Data.Singletons.Prelude.Const
->Data.Functor.Const.Singletons
Data.Singletons.Prelude.Either
->Data.Either.Singletons
Data.Singletons.Prelude.Enum
->Data.Singletons.Base.Enum
Data.Singletons.Prelude.Eq
->Data.Eq.Singletons
Data.Singletons.Prelude.Foldable
->Data.Foldable.Singletons
Data.Singletons.Prelude.Function
->Data.Function.Singletons
Data.Singletons.Prelude.Functor
->Data.Functor.Const.Singletons
Data.Singletons.Prelude.Identity
->Data.Functor.Identity.Singletons
Data.Singletons.Prelude.IsString
->Data.String.Singletons
Data.Singletons.Prelude.Ord
->Data.Ord.Singletons
Data.Singletons.Prelude.List
->Data.List.Singletons
Data.Singletons.Prelude.List.NonEmpty
->Data.List.NonEmpty.Singletons
Data.Singletons.Prelude.Maybe
->Data.Maybe.Singletons
Data.Singletons.Prelude.Monad
->Control.Monad.Singletons
Data.Singletons.Prelude.Monad.Fail
->Control.Monad.Fail.Singletons
Data.Singletons.Prelude.Monad.Zip
->Control.Monad.Zip.Singletons
Data.Singletons.Prelude.Monoid
->Data.Monoid.Singletons
Data.Singletons.Prelude.Proxy
->Data.Proxy.Singletons
Data.Singletons.Prelude.Semigroup
->Data.Semigroup.Singletons
Data.Singletons.Prelude.Show
->Data.Show.Singletons
Data.Singletons.Prelude.Traversable
->Data.Traversable.Singletons
Data.Singletons.Prelude.Tuple
->Data.Tuple.Singletons
Data.Singletons.Prelude.Void
->Data.Void.Singletons
Data.Singletons.TH
->Data.Singletons.Base.TH
Data.Singletons.TypeError
->Data.Singletons.Base.TypeError
Data.Singletons.TypeLits
->GHC.TypeLits.Singletons
Data.Singletons.TypeRepTYPE
->Data.Singletons.Base.TypeRepTYPE
Note that modules that do not correspond to any particular module in
base
now have the prefixData.Singletons.Base.*
. This includesData.Singletons.Base.Enum
, a special module that exists to provide a home for theSucc
andPred
promoted type families that is separate fromPrelude.Singletons
(which exports everything fromPEnum
exceptSucc
andPred
). This is done in an effort to make importingPrelude.Singletons
less likely to induce name clashes with code that works over unary natural numbers, which often use the names "Succ
" and "Pred
". -
An effort has been made to make the API of
Prelude.Singletons
more closely mirror that of thePrelude
inbase
. As a result,Prelude.Singletons
now exports some different functions than it used to. In particular, it now exports the following:Until
/sUntil
/UntilSym{N}
type (++@#@$$$)
type (.@#@$$$$)
FlipSym3
type (!!)
/(%!!)
/type (!!@#@{$})
Length
/sLength
/LengthSym{N}
DropWhile
/sDropWhile
LookupSym{N}
Unzip3Sym{N}
Prelude.Singletons
also used to export some things that were not exported by thePrelude
. Accordingly, these exports have been removed fromPrelude.Singletons
. They are:(^)
/(%^)
/type (^@#@{$})
. Although thePrelude
does define a function named(^)
, it is more general than the one defined insingletons-base
, which only works onNat
s. ImportGHC.TypeLits.Singletons
if you wish to use theNat
-specific versions.DefaultEq
, which has no counterpart in thePrelude
. ImportData.Eq.Singletons
if you wish to use this.bool_
, which has no counterpart in thePrelude
. ImportData.Bool.Singletons
if you wish to use this.
-
Two previously public-facing modules—
Data.Singletons.Prelude.Base
andData.Singletons.Prelude.Num
—have been turned into internal modules. The contents of these modules are re-exported fromPrelude.Singletons
, so that can be used instead. -
Due to the
singletons
package split, theEq
,Ord
, etc. instances forSomeSing
are no longer provided in theData.Singletons
module in thesingletons
library. Instead, they are now provided in a newData.Singletons.Base.SomeSing
module, which definesEq
,Ord
, etc. instances forSomeSing
as orphans. -
The
PEq
class no longer usesDefaultEq
as its default implementation for(==)
.DefaultEq
, despite its name, is actually not a suitable implementation for(==)
for a good majority of singleton types (see the discussion in this GitHub issue for more information).(==)
's default is now defined in terms of(/=)
, just like its term-level counterpart in theEq
class. -
Since
base-4.15.0.0
now deprecatesData.Singletons.Option
(in anticipation of its removal in a future version ofbase
), this library no longer offers a singleton type forOption
. Accordingly, theoption_
function has also been removed.