Extensible records for Haskell with lenses.
FieldRec: records with named fields. We now take advantage of the
-XOverloadedLabelsextension to support referring to record fields by names such a
ARectype for constant-time field access. You can convert a classic, HList-like
toARec, or back the other way with
Arrayto 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
=: 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.
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
b, or a
c. In contrast a
Rec [a,b,c] includes an
b, and, a
Added a concise
Show instance for
Ported the tutorial to haddocks (andrewthad)
Added utilities for working with the
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.
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