Data.Record.Encode

This library provides generic machinery (via GHC.Generics and `generics-sop`) to encode values of some algebraic type as points in a vector space.

Processing datasets that have one or more categorical variables (which in other words are values of a sum type) typically requires a series of boilerplate transformations, and the encodeOneHot function provided here does precisely that.

Internals

This library makes use of generic programming to analyze both values and types (see the internal Data.Record.Encode.Generics module).

Initially, it was relying on Template Haskell to analyze types, using the the instance generation machinery explained here: https://markkarpov.com/tutorial/th.html#example-1-instance-generation

One-hot encoding

encodeOneHot :: forall a. G a => a -> Vector Int

Computes the one-hot encoding of a value of a sum type.

The type of the input value must be an instance of Generic (from GHC.Generics) and of Generic (from the `generics-sop` library).

>>> :set -XDeriveGeneric

>>> import qualified GHC.Generics as G
>>> import qualified Generics.SOP as SOP
>>> import Data.Record.Encode

>>> data X = A | B | C deriving (G.Generic)
>>> instance SOP.Generic X

>>> encodeOneHot B
[0,1,0]

type G a = (GVariants (Rep a), Generic a, Generic a)

Constraints necessary to encodeOneHot a value.

NB: GVariants is an internal typeclass, and this constraint is automatically satisfied if the type is an instance of Generic