anchor.diff:  			io:format(user, "\nINVALID INPUT\n", []),
   			false
   	end.
  +
  +diamond() -> 
  +	io:format(user, "\nINVALID INPUT\n", []),
  +	false.	
   
   -ifdef(TEST).
   
  
positive.code: 	CleanSpec = re:replace(TrimmedSpec, "[^A-Za-z]", "", [global, {return,list}]),
  	(CleanSpec =:= TrimmedSpec) and (length(CleanSpec) == 1).
  
  diamond(Spec) -> 
  	ValidSpec = is_valid_spec(Spec),
      if
      	ValidSpec ->
  
negative.code: positive_smoke_test() ->
      ?assert(diamond(['Z'])).
  
  negative_smoke_test_() ->
  	[
      	?_assertNot(diamond([";"])),
      	?_assertNot(diamond())
      ].
  
  -endif.