anchor.diff:                                 if-invalid
                                  parser
                                  completer
  +			       type
                                  (color *prompt-color*)
                                  (error-color *prompt-error-color*))
     "Prompt for a string.
  
positive.code:                       (if if-invalid
                            (funcall (parse-if-invalid if-invalid error-color) parsed-input)
                            (say "The value is not valid" :color error-color)))
                       (t
                        (return parsed-input))))))))))
  
  
negative.code:          - 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 ()
  