POPLEVEL

The POPLEVEL command restores all values saved with PUSH commands that were executed since the last POPLEVEL command specifying the same marker.

You must use PUSHLEVEL to mark a starting point for a series of PUSH commands before you can use POPLEVEL to restore the saved values. POPLEVEL itself marks the end of the series. You can use POPLEVEL only within programs. (Abbreviated PPL.)

Syntax

POPLEVEL marker-expression [DISCARD]

Arguments

marker-expression

A text value used as a marker. This must be exactly the same as the value used in the corresponding PUSHLEVEL command to mark the start of a series of saved values being popped.

DISCARD

Specifies that the pushed values for that level are discarded when you issue the POPLEVEL command. When you do not specify DISCARD, the values that were pushed are used to reset the pushed objects.

Notes

POPLEVEL and PUSH

Two possible uses for the POPLEVEL command are:

• After a series of increasingly broadening or narrowing LIMIT commands, each with a corresponding PUSH.

• After a single extremely long and complicated PUSH command, or a series of short ones given throughout a program, that may need a lot of editing. PUSHLEVEL and POPLEVEL allow you to edit the arguments for a long and complicated PUSH command without also having to edit a corresponding long and complicated POP command.

Nesting

You can nest PUSHLEVEL and POPLEVEL pairs, as long as you specify a different marker for each pair.

Duplicate Markers

When you specify the same marker for two or more PUSHLEVEL commands, a POPLEVEL command specifying that same marker will restore values that were saved only since the most recent PUSHLEVEL command.

Multiple PUSHLEVEL Commands

When you specify a different marker for two or more PUSHLEVEL commands, a POPLEVEL command that specifies the marker of any PUSHLEVEL command restores all the values that were saved since that command, including values that were saved after later PUSHLEVEL commands.

Related Statements

POP, PUSH, PUSHLEVEL, and CONTEXT command.

Examples

To see a sample program using POPLEVEL, see the PUSHLEVEL example.