This module provides convenient TemplateHaskell functions for making type lens suitable for use with multivariate distributions.

Given a data type that looks like:

data Character = Character
    { _name      :: String
    , _species   :: String
    , _job       :: Job
    , _isGood    :: Maybe Bool
    , _age       :: Double -- in years
    , _height    :: Double -- in feet
    , _weight    :: Double -- in pounds
    }
    deriving (Read,Show,Eq,Ord)
 
data Job = Manager | Crew | Henchman | Other
    deriving (Read,Show,Eq,Ord)

when we run the command:

makeTypeLenses ''Character

We generate the following type lenses automatically:

data TH_name    = TH_name
data TH_species = TH_species
data TH_job     = TH_job
data TH_isGood  = TH_isGood
data TH_age     = TH_age
data TH_height  = TH_height
data TH_weight  = TH_weight

instance TypeLens TH_name where
    type instance TypeLensIndex TH_name = Nat1Box Zero
instance TypeLens TH_species where
    type instance TypeLensIndex TH_species = Nat1Box (Succ Zero)
instance TypeLens TH_job where
    type instance TypeLensIndex TH_job = Nat1Box (Succ (Succ Zero))
instance TypeLens TH_isGood where
    type instance TypeLensIndex TH_isGood = Nat1Box (Succ (Succ (Succ Zero)))
instance TypeLens TH_age where
    type instance TypeLensIndex TH_age = Nat1Box (Succ (Succ (Succ (Succ Zero))))
instance TypeLens TH_height where
    type instance TypeLensIndex TH_height = Nat1Box (Succ (Succ (Succ (Succ (Succ Zero)))))
instance TypeLens TH_weight where
    type instance TypeLensIndex TH_weight = Nat1Box (Succ (Succ (Succ (Succ (Succ (Succ Zero))))))
        
instance Trainable Character where
    type instance GetHList Character = HList '[String,String,Job,Maybe Bool, Double,Double,Double]
    getHList var = name var:::species var:::job var:::isGood var:::age var:::height var:::weight var:::HNil

instance MultivariateLabels Character where
    getLabels dist = ["TH_name","TH_species","TH_job","TH_isGood","TH_age","TH_height","TH_weight"]