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.




 
Module Checkit {
      function f$ {
            what$=mid$(trim$(letter$),2)
            what$=Left$(what$, len(what$)-1)
            flush ' erase any argument from stack
            Data param$(what$)
            m=stack.size
            document resp$="{" 
             if m>2 then {
                  shift m-1, 2    ' get last two as first two
                  push letter$+" and "+letter$
                  m--   ' one less
                  shiftback m   ' move to last position
            }
            while not empty {
                   resp$=letter$+if$(not empty->", ", "")
             }
            =resp$+"}"   
 
      }
      \\ we use ? for Print
      ? f$({[]})
      ? f$({["ABC"]})
      ? f$({["ABC", "DEF"]})
      ? f$({["ABC","DEF", "G", "H"]})
}
Checkit
 