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' This example uses a recursive FUNCTION procedure (a function that calls
' itself) to find and return the length of a string. The CALL statement is
' then used to call a SUB procedure that prints a message on the 25th line
' of the display.
 
' To try this example:
' 1. Choose New Project from the File menu
' 2. Copy the code example below to the code window
' 3. Press F5 to run the example
 
 DECLARE FUNCTION StrgLng% (X$)
 DECLARE SUB PrintMessage (message$)
 CLS                             ' Clear the screen
 INPUT "Enter a string: ", InString$
 length% = StrgLng%(InString$)
 message$ = "The length of the string is" + STR$(length%)
 CALL PrintMessage(message$)
 
 SUB PrintMessage (message$)
     LOCATE 24, 1
     PRINT message$;
 END SUB
 
 FUNCTION StrgLng% (X$)
     IF X$ = "" THEN
          ' The length of a null string is zero
          StrLng% = 0
     ELSE
          ' Non-null string - make a recursive call
          ' The length of a non-null string is 1 plus
          ' the length of the rest of the string
          StrgLng% = 1 + StrgLng%(MID$(X$, 2))
     END IF
 END FUNCTION