vinyl
Extensible Records
Version on this page: | 0.10.0.1 |
LTS Haskell 22.41: | 0.14.3 |
Stackage Nightly 2024-11-12: | 0.14.3 |
Latest on Hackage: | 0.14.3 |
vinyl-0.10.0.1@sha256:283c57a997f0a3e4d4713f64e1f1998923b2d9a8f4c81b7145bba54efa09b5e9,3792
Module documentation for 0.10.0.1
- Data
- Data.Vinyl
Extensible records for Haskell with lenses.
Changes
0.10.0
-
Changed the types of
Data.Vinyl.CoRec.onCoRec
andData.Vinyl.CoRec.onField
. This was pushing through the changes to drop the use ofProxy
arguments, relying instead onTypeApplications
. Also addedonCoRec1
andonField
to work with functions relying on a single type class. -
Faster
asA
andasA'
. These implementations utilizeunsafeCoerce
in their implementations after we have performed a runtime check that proves (to us) that the types match up. The old implementations are still available asasASafe
andasA'Safe
. While both implementations can run in constant time if the compiler optimizes everything successfully, the faster variants are a bit more than 3x faster in a trivial benchmark. -
Add a
Generic
instance forRec
and common functors. -
Add a variety of
ToJSON
implementations as a test case. One or all of these should probably exist as a separate package to avoidvinyl
depending onaeson
, but their content may be of interest.
0.9.2
- Add
runcurryX
for applying an uncurried function to aRec
passing through theXRec
machinery to strip out syntactic noise.
0.9.0
-
A new
SRec
type for constant time field access for records with densely packedStorable
fields. Conversion fromRec
is accomplished withtoSRec
, whilefromSRec
takes you back toRec
. Record updates are fairly slow compared to native Haskell records and evenRec
, but reading a field is as fast as anything. -
Concise record construction syntax from tuples. Construct a
FieldRec
withfieldRec (#x =: True, #y =: 'b')
and have the type inferred asRec ElField '[ '("x", Bool), '("y", Char) ]
. Or userecord
to build records of any functor. Thanks to @heptahedron on GitHub for prompting this feature, and @sboosali for thinking through various approaches. -
Optional concise record field lens syntax. This uses an orphan
IsLabel
instance for all function types, so will conflict with any other library that does the same. Thus it is entirely opt-in: to enable this syntax, you must explicitlyimport Data.Vinyl.Syntax
. This enables the use of labels as lenses. For example,myRec & #name %~ map toUpper
to applymap toUpper
to the#name
field of the record valuemyRec
. This technique is thanks to Tikhon Jelvis who shared it on the Haskell-Cafe mailing list. -
Field lenses can now change the type of a record. Thanks to @heptahedron on GitHub for exploring this feature. Using the above-mentioned features, one might now write something like
myRec & #name %~ length
to produce a record whose#name
field is the length of theString
#name
field of some record value,myRec
. -
Changed the type of
=:=
again to work directly withLabel
s as this is the most convenient usage. -
Definitions in
Data.Vinyl.Core
are now consistently in terms of type classes. This permits inlining and specialization to a user’s record types. In the case where the record type is known, call sites do not change. But for functions polymorphic in the record’s fields, a constraint will be required. If those constraints are a nuisance, or compile times increase beyond comfort, users should use definitions from theData.Vinyl.Recursive
that are written in a recursive style (as in previous versions of thevinyl
package), treating the record as a list of fields. -
Added
restrictCoRec
andweakenCoRec
suggested by @ElvishJerricco
0.8.0
-
Overhaul of
FieldRec
: records with named fields. We now take advantage of the-XOverloadedLabels
extension to support referring to record fields by names such a#myField
. -
A new
ARec
type for constant-time field access. You can convert a classic, HList-likeRec
into anARec
withtoARec
, or back the other way withfromARec
. AnARec
uses anArray
to store record fields, so the usual trade-offs between lists and arrays apply: lists are cheap to construct by adding an element to the head, but slow to access; it is expensive to modify the shape of an array, but element lookup is constant-time.
Compatibility Break: The operator =:
for constructing a record with a single field has changed. That operation is now known as =:=
, while =:
is now used to construct an ElField
. It was decided that single-field record construction was not a common use-case, so the shorter name could be used for the more common operation. Apologies for making the upgrade a bit bumpy.
0.7.0
- Simplified
match
- Added
Data.Vinyl.Curry
0.6.0
Added a CoRec
(co-record) type constructed in the same style as the existing Rec
type for records. A CoRec
is an open sum type: a value of CoRec [a,b,c]
is either an a
, a b
, or a c
. In contrast a Rec [a,b,c]
includes an a
, a b
, and, a c
.
0.5.3
Added a concise Show
instance for Const
.
0.5.2
Ported the tutorial to haddocks (andrewthad)
0.5.1
Added utilities for working with the FieldRec
type.
0.5
Vinyl 0.5 combines the generality of Vinyl 0.4 with the ease-of-use of previous versions by eschewing the defunctionalized type families and just using plain type constructors; Vinyl 0.4-style records can be recovered in most cases in a modular manner without baking it into the fabric of Vinyl itself.
Also new in 0.5 is a unified lens-based approach to subtyping, coercion and projection.
0.4
Vinyl 0.4 is a big departure from previous versions, in that it introduces a universe encoding as a means to generalize the space of keys from strings to any arbitrary space. This means that you can have closed universes for your records.
For details on how to use the new Vinyl, please see tests/Intro.lhs
or view
Jon’s talk at BayHac 2014, Programming in
Vinyl.