Comma quibbling is a task originally set by Eric Lippert in his blog.



Task

Write a function to generate a string output which is the concatenation of input words from a list/sequence where:

 An input of no words produces the output string of just the two brace characters "{}".
 An input of just one word, e.g. ["ABC"], produces the output string of the word inside the two braces, e.g. "{ABC}".
 An input of two words, e.g. ["ABC", "DEF"], produces the output string of the two words inside the two braces with the words separated by the string " and ", e.g. "{ABC and DEF}".
 An input of three or more words, e.g. ["ABC", "DEF", "G", "H"], produces the output string of all but the last word separated by ", " with the last word separated by " and " and all within braces; e.g. "{ABC, DEF, G and H}".


Test your function with the following series of inputs showing your output here on this page:

 [] # (No input words).
 ["ABC"]
 ["ABC", "DEF"]
 ["ABC", "DEF", "G", "H"]


Note: Assume words are non-empty strings of uppercase characters for this task.




to join :delimiter :list [:result []]
  output cond [
    [ [empty? :list]   :result ]
    [ [empty? :result] (join :delimiter butfirst :list first :list) ]
    [ else             (join :delimiter butfirst :list 
                                        (word :result :delimiter first :list)) ]
  ]
end
 
to quibble :list
  local "length
  make "length count :list
  make "text (
    ifelse [:length <= 2] [
      (join "\ and\  :list)
    ] [ 
      (join "\ and\  (sentence join ",\  butlast :list last :list))
    ])
  output ifelse [empty? :text] "\{\} [(word "\{ :text "\})]
end
 
foreach [ [] [ABC] [ABC DEF] [ABC DEF G H] ] [
  print quibble ?
]
 
bye