Compaq AA-PWCBD-TE manual Simple Programs, Complex Programs, Example 5-1 Show Summary Display

DEC Text Processing Utility Program Development

5.1Creating DECTPU Programs

•You can use executable statements either within procedures or outside procedures. You must place all procedure declarations before any executable statements that are not in procedures.

•You can enter DECTPU statements from within EVE by using the EVE command TPU. For more information on using this command, see the Extensible Versatile Editor Reference Manual.

5.1.1 Simple Programs

The following statement is an example of a simple program:

SHOW (SUMMARY);

The preceding statement, entered after the appropriate prompt from your editor, causes DECTPU to execute the program associated with the SHOW (SUMMARY) statement. If you use EVE with a user-written command file, your screen may display text similar to Example 5–1.

Example 5–1 SHOW (SUMMARY) Display
DECTPU V3.1	1993-08-17	08:37
Journal file:
Section file name: EVE$SECTION			Ident: V3.1	Date: 17-AUG-1993 08:49
Activated from: TPU$SECTION
Created by: DECTPU V3.1			1993-08-17 08:37
Extension: SCREEN_UPDATER		Ident: DECTPU V3.1		1993-08-17 08:37
Timer Message:	working
24 System buffers and 1		User buffer

5.1.2 Complex Programs

When writing complex DECTPU programs, avoid the following practices:

•Creating large procedures

•Creating large number of procedures

•Including a large number of executable statements that are not within procedures

These practices, if carried to extremes, can cause the parser stack to overflow.

The DECTPU parser currently allows a maximum stack depth of 1000 syntax tree nodes. When the parser first encounters a DECTPU statement, the parser assigns each token in the statement to a syntax tree node. For example, the statement ‘‘a := 1’’ contains three tokens, each of which occupies a syntax tree node. After the parser parses this statement, only the assignment statement remains on the stack of nodes. The a and the 1 are subtrees to the assignment syntax tree node.

The most common cause of stack overflow, which is signaled by the status TPU$_ STACKOVER, is creating one or more large procedures whose statements occupy too many syntax tree nodes. To make your program manageable by the parser, break the large procedures into smaller ones.

5–2DEC Text Processing Utility Program Development