type: keyword location: built-in source file: xlread.c Common LISP compatible: no supported on: all machines
:MESCAPE is an entry that is used in the *READTABLE*. *READTABLE* is a system variable that contains XLISP's data structures relating to the processing of characters from the user (or files) and read-macro expansions. The existance of the :MESCAPE keyword means that the specified character is to be used as a multiple escape character. The system defines that the the vertical bar character | is the only :MESCAPE character.
(defun look-at (table) ; define a function to (dotimes (ch 127) ; look in a table (prog ( (entry (aref table ch)) ) ; and print out any (case entry ; entries with a function (:MESCAPE ; (princ (int-char ch))) ; (T NIL)))) ; (terpri)) ; (look-at *readtable*) ; prints |
CAUTION: If you experiment with *READTABLE*, it is useful to save the old value in a variable, so that you can restore the system state.