anchor.diff:           - if-invalid(function): Function to execute if the validator fails.
            - parser (function): A function to parse the input string.
            - completer: A custom completer. Default: no completion.
  +         - type: Type expected.
            - color: Prompt color
            - error-color: Prompt error color."
     (flet ((read-input ()
  
positive.code:                                if-invalid
                                 parser
                                 completer
                                 (color *prompt-color*)
                                 (error-color *prompt-error-color*))
    "Prompt for a string.
  
negative.code:                       (if if-invalid
                            (funcall (parse-if-invalid if-invalid error-color) parsed-input)
                            (say "The value is not valid" :color error-color)))
  		     ((and type (not (typep parsed-input type)))
  		      (if if-invalid
  			  (funcall (parse-if-invalid if-invalid error-color) parsed-input)
  			  (say "Value should be of type: ~a" type :color error-color)))			   
                       (t
                        (return parsed-input))))))))))
  
  