« Changelog History


vinyl v0.9.0 Release Notes

    • ⚡️ A new SRec type for constant time field access for records with densely packed Storable fields. Conversion from Rec is accomplished with toSRec, while fromSRec takes you back to Rec. Record updates are fairly slow compared to native Haskell records and even Rec, but reading a field is as fast as anything.

    • 🏗 Concise record construction syntax from tuples. Construct a FieldRec with fieldRec (#x =: True, #y =: 'b') and have the type inferred as Rec ElField '[ '("x", Bool), '("y", Char) ]. Or use record 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 explicitly import Data.Vinyl.Syntax. This enables the use of labels as lenses. For example, myRec & #name %~ map toUpper to apply map toUpper to the #name field of the record value myRec. 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 with Labels 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 the Data.Vinyl.Recursive that are written in a recursive style (as in previous versions of the vinyl package), treating the record as a list of fields.

    • ➕ Added restrictCoRec and weakenCoRec suggested by @ElvishJerricco