The $STACK special variable contains the current number of context frames on the call stack. QUIT clears all levels from the program stack. If n resolves to 0 (zero), the system generates a error. If n resolves to a negative non-zero integer, QUIT clears all levels from the program stack. A fractional number for n is truncated to its integer value. If n is larger than the current number of levels, all levels are cleared from the program stack and no error is issued. You can specify n as a literal, a variable, or an arithmetic expression. You can use the $STACK special variable to determine the current number of levels on the program stack. QUIT n clears the specified number of levels from the program stack. Issuing a QUIT at the Terminal prompt clears entities from the program stack. The same behavior occurs if the subroutine was called by DO terminated by an argumented QUIT, and the subroutine is terminated by an $ETRAP. For example, a subroutine called by DO that concludes with QUIT 4/0 generates a error. If the subroutine was called by a DO command and is in the scope of that DO argument, then the QUIT command evaluates its argument (and any side effects of that evaluation occur), but it does not return the argument. Execution returns to the caller of the subroutine. If an argumented QUIT is invoked inside a subroutine (instead of a function), the QUIT argument is evaluated (which may produce side effects or throw an error) and the argument result is discarded. If an argumented QUIT is invoked inside a subroutine, one of the following occurs: QUIT with an argument also cannot be used to exit from within a TRY block or a CATCH block. QUIT with an argument cannot be used to exit a routine from within a FOR, DO WHILE, or WHILE command loop.
QUIT expression terminates a user-defined function or an object method and returns the value resulting from the specified expression. If the terminated operation contains any NEW commands before QUIT, QUIT automatically KILLs the affected variables and restores them to their original values. If DO, XECUTE, or an (unnested) flow-of-control loop command was issued from the Terminal prompt, QUIT returns control to the Terminal. It is used to terminate the execution level of a process started with a DO or XECUTE command, or to exit from a FOR, DO WHILE, or WHILE flow-of-control loop. QUIT without an argument exits from the current context without returning a value. Two $ECODE error codes are provided for this purpose: M16 “Quit with an argument not allowed” and M17 “Quit with an argument required.” QUIT Without an Argument The $QUIT special variable indicates whether or not an argumented QUIT command is required to exit from the current context. RETURN always exits the current routine, returning to the calling routine or terminating the program if there is no calling routine.Ī postconditional is not considered an argument. The similar RETURN command terminates execution of a routine at any point, including from within a FOR, DO WHILE, or WHILE loop or nested loop structure, or a TRY or CATCH block.
When invoked from within a FOR, DO WHILE, or WHILE flow-of-control structure, or a TRY or CATCH block, the QUIT breaks out of the structure and continues execution with the next command outside of that structure. When invoked in a routine, QUIT returns to the calling routine, or terminates the program if there is no calling routine. The QUIT command terminates execution of the current context, exiting to the enclosing context. The QUIT command is used in two different contexts: Optional - Terminal prompt only: The number of program levels to clear an expression that resolves to a positive integer. Optional - A value to return to the invoking routine a valid expression.
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