yoko: Generic Programming with Disbanded Data Types
Based off of the paper "A Pattern for Almost Compositional Functions" at http://www.ittc.ku.edu/~nfrisby/papers/yoko.pdf, submitted to ICFP 2012.
yoko views a nominal datatype as a band of constructors, each
a nominal type in its own right. Such datatypes can be disbanded via the
disband function into an anonymous sum of nominal constructors, and vice
versa via the
band function. This library uses extensive type-level
programming to enrich its
instant-generics foundation with capabilities
derived from the constructor-centric perspective.
For example, consider the following nominal datatype.
data Beatles = John ... | Paul ... | George ... | Ringo ...
This type can of course be understood as a sum of the individual constructor types.
data John = John ... data Paul = Paul ... data George = George ... data Ringo = Ringo ...
yoko's conceptual foundations start there. In particular, this allows a
John, to be used independently of its original range type
and sibling constructors.
As a generic programming library,
support for constructor-centric generic programming. The
file distributed with the
yoko source demonstrates defining a
lambda-lifting conversion between the two types
ULC, which has lambdas,
Prog, which has top-level function declarations instead.
data ULC = Lam Type ULC | Var Int | Let [Decl] ULC | App ULC ULC data Decl = Decl Type ULC data Prog = Prog [FunDec] TLF type FunDec = ([Type], [Type], Type, TLF) data TLF = Top Int [Occ] | Occ Occ | App TLF TLF data Occ = Par Int | Env Int
These types are defined in separate modules, since they have constructors
with the same name. Indeed, the fact that they having matching constructors
App is crucial for
yoko's automatic conversion from
App. As written, the generic lambda-lifter would continue to
work for any new
ULC constructors (e.g. syntax for tuples or mutable
references) as long as constructors with the same names and analogous fields
were added to
TLF and the semantics of those constructors doesn't involve
binding. This default behavior of the lambda-lifter is specified in about ten
lines of user code.
Existing generic libraries don't use constructor names to the degree that
yoko does, and so cannot accomodate generic conversions as well.
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|Versions||0.1, 0.2, 0.3, 0.3.0.1, 0.3.1, 0.3.1.1, 0.3.1.2, 0.3.1.3, 0.3.2, 0.3.2.1, 0.3.2.2, 0.9, 2.0|
|Dependencies||base (==4.*), tagged-th (<0.2), template-haskell, type-booleans (<0.2), type-cereal (<0.2), type-digits (<0.2), type-equality (<0.2), type-ord (<0.2), type-ord-spine-cereal (<0.2), type-spine (<0.2) [details]|
|Author||Nicolas Frisby <firstname.lastname@example.org>|
|Maintainer||Nicolas Frisby <email@example.com>|
|Uploaded||by NicolasFrisby at Tue Mar 13 08:34:32 UTC 2012|
|Downloads||4037 total (23 in the last 30 days)|
|Rating||(no votes yet) [estimated by rule of succession]|
|Status||Docs uploaded by user
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