swift_lemma.swift

let text = "swimming, swam, swim, assuming, assumed, assume, learned, learning."

// Initialize the NLTagger with scheme type as "lemma"
let tagger = NLTagger(tagSchemes: [.lemma])
// Set the string to be processed
tagger.string = text
// Loop over all the tokens and print their lemma
tagger.enumerateTags(in: text.startIndex..<text.endIndex, unit: .word, scheme: .lemma) { tag, tokenRange in
  if let tag = tag {
      print("\(text[tokenRange]): \(tag.rawValue)")
  }
  return true
}