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.




$ include "seed7_05.s7i";
 
const func string: quibble (in array string: input) is func
  result
    var string: quibble is "{";
  begin
    case length(input) of
      when {0}:  quibble &:= "}";
      when {1}:  quibble &:= input[1] & "}";
      otherwise: quibble &:= join(input[.. pred(length(input))], ", ") &
                             " and " & input[length(input)] & "}";
    end case;
  end func;
 
const proc: main is func
  begin
    writeln(quibble(0 times ""));
    writeln(quibble([] ("ABC")));
    writeln(quibble([] ("ABC", "DEF")));
    writeln(quibble([] ("ABC", "DEF", "G", "H")));
  end func;