Predicates for Strings
For more information about general sequence and array predicates, see Sequences, Arrays, and Vectors, and Arrays.
Function: stringp object
This function returns t if object is a string, nil otherwise.
Function: string-or-null-p object
This function returns t if object is a string or nil. It returns nil otherwise.
Function: char-or-string-p object
This function returns t if object is a string or a character (i.e., an integer), nil otherwise.