set-macro-character, get-macro-characterFunction


    get-macro-character char &optional readtable function, non-terminating-p

    set-macro-character char new-function &optional non-terminating-p readtable t

    Arguments and Values

    char — a character.

    non-terminating-p — a generalized boolean. The default is false.

    readtable — a readtable designator. The default is the current readtable.

    functionnil, or a designator for a function of two arguments.

    new-function — a function designator.


    get-macro-character returns as its primary value, function, the reader macro function associated with char in readtable (if any), or else nil if char is not a macro character in readtable. The secondary value, non-terminating-p, is true if char is a non-terminating macro character; otherwise, it is false.

    set-macro-character causes char to be a macro character associated with the reader macro function new-function (or the designator for new-function) in readtable. If non-terminating-p is true, char becomes a non-terminating macro character; otherwise it becomes a terminating macro character.

    (get-macro-character #\{)  NIL, false 
    (not (get-macro-character #\;))  false

    The following is a possible definition for the single-quote reader macro in standard syntax:

    (defun single-quote-reader (stream char) 
      (declare (ignore char)) 
      (list 'quote (read stream t nil t)))  SINGLE-QUOTE-READER 
    (set-macro-character #\' #'single-quote-reader)  T

    Here single-quote-reader reads an object following the single-quote and returns a list of quote and that object. The char argument is ignored.

    The following is a possible definition for the semicolon reader macro in standard syntax:

    (defun semicolon-reader (stream char) 
      (declare (ignore char)) 
      ;; First swallow the rest of the current input line. 
      ;; End-of-file is acceptable for terminating the comment. 
      (do () ((char= (read-char stream nil #\Newline t) #\Newline))) 
      ;; Return zero values. 
      (values))  SEMICOLON-READER 
    (set-macro-character #\; #'semicolon-reader)  T
    Side Effects

    The readtable is modified.

    See Also