An experiment with the lambda.r R package (Haskell and R code)

experiment.hs

data FruitSet =
        LAS
    |   SAS
    |   OFS
    deriving (Eq, Show)

fSMergeList :: [FruitSet] -> Bool -> FruitSet
fSMergeList (x:xs) intersect = foldr (\a b -> fSMerge a b intersect) x xs

fSMerge :: FruitSet -> FruitSet -> Bool -> FruitSet
fSMerge LAS LAS _     = LAS
fSMerge SAS SAS _     = SAS
fSMerge OFS _   _     = OFS
fSMerge _   OFS _     = OFS
fSMerge LAS SAS True  = SAS
fSMerge SAS LAS True  = SAS
fSMerge LAS SAS False = LAS
fSMerge SAS LAS False = LAS

experiment.R

library(lambda.r)

FruitSet("LAS") %as% "LAS"
FruitSet("SAS") %as% "SAS"
FruitSet("OFS") %as% "OFS"

FruitSetList(...) %::% FruitSet... : FruitSetList
FruitSetList(...) %as% asFruitSetList(list(...))

asFruitSetList(xs) %::% list : FruitSetList
asFruitSetList(xs) %as% { 
  class(xs) <- c("FruitSetList")
  xs
}

fsMerge(a, b, intersect) %::% FruitSet : FruitSet : logical : FruitSet
fsMerge("LAS", "LAS", intersect) %as% FruitSet("LAS")
fsMerge("SAS", "SAS", intersect) %as% FruitSet("SAS")
fsMerge("OFS", b,     intersect) %as% FruitSet("OFS")
fsMerge(a,     "OFS", intersect) %as% FruitSet("OFS")
fsMerge("LAS", "SAS", TRUE     ) %as% FruitSet("SAS")
fsMerge("SAS", "LAS", TRUE     ) %as% FruitSet("SAS")
fsMerge("LAS", "SAS", FALSE    ) %as% FruitSet("LAS")
fsMerge("SAS", "LAS", FALSE    ) %as% FruitSet("LAS")

fsMergeList(xs, intersect) %::% FruitSetList : logical : FruitSet
fsMergeList(xs, intersect) %as% 
  Reduce(
    function(a, b) { fsMerge(a, b, intersect) }, 
    xs[tail(seq_along(xs), n = -1)], 
    init = xs[[1]]
  )