ECLAT Frequent Pattern Matching in Swift

eclat.swift

var accumulatedItemSets = Dictionary(uniqueKeysWithValues: database.map {
    (Set([$0.key]), Set($0.value)) })
var itemSetsToEvaluate = accumulatedItemSets

while !itemSetsToEvaluate.isEmpty {
    var temp: [Set<String>: Set<Int>] = [:]
    itemSetsToEvaluate.pairs().forEach { a, b in
        let key = a.key.union(b.key)
        let value = a.value.intersection(b.value)
        if value.count >= absoluteSupport {
            temp[key] = value
        }
    }
    accumulatedItemSets.merge(temp) { $1 }
    itemSetsToEvaluate = temp
}