Q12074: CLEAR Should Not Be Used in Event Trap

Article: Q12074
Product(s): See article
Version(s): 2.00 2.01 3.00 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | B_BasicCom | mspl13_basic
Last Modified: 4-JAN-1990

The presence of a CLEAR statement in the following event handling
routine generates an "Illegal function call" error at compile time:

      CLEAR ,,800
      KEY(2) ON
      ON KEY(2) GOSUB 200
      WHILE INKEY$="" : WEND
      PRINT "this is a test"
      END
  200 CLEAR ,,800
      PRINT "this worked"
      RETURN

The error occurs because the CLEAR statement changes the stack. The
CLEAR statement is not allowed in an event handler because it would
destroy the return address.