Compaq AA-PWCBD-TE manual Example 4-8 Recursive Procedure, Local Variables, Constants

Lexical Elements of the DEC Text Processing Utility Language 4.9 Reserved Words

Example 4–8 Recursive Procedure

PROCEDURE user_reverse

LOCAL temp_string;

temp_string := READ_LINE("input>");

	! Read a response
IF temp_string <> " "	! Quit if nothing entered
THEN	! but the RETURN key.
user_reverse	! Call user_reverse recursively
ELSE
RETURN	! All done, go to display lines
ENDIF;
MESSAGE (temp_string);	! Display lines typed in reverse order
ENDPROCEDURE;	! in the message window

4.9.4.7 Local Variables

The use of local variables in procedures is optional. If you use local variables, they hold the values that you assign them only in the procedure in which you declare them. The maximum number of local variables that you can use is 255. Local variables are initialized to 0.

Syntax

LOCAL variable-name [[,...]];

If you declare a local variable in a procedure and, in the same procedure, use the EXECUTE built-in to assign a value to a variable with the same name as the local variable, the result of the EXECUTE built-in has no effect on the local variable. Consider the following code fragment:

PROCEDURE test

LOCAL X;

EXECUTE ("X := 3");

MOVE_VERTICAL (X);

ENDPROCEDURE;

In this fragment, when the compiler evaluates the string "X := 3", the compiler assumes X is a global variable. The compiler creates a global variable X (if none exists) and assigns the value 3 to the variable. When the MOVE_VERTICAL built-in procedure uses the local variable X, the local variable has the value 0 and the MOVE_VERTICAL built-in has no effect.

Local variables may also be declared in unbound code. See Section 4.9.5.2.

4.9.4.8 Constants

The use of constants in procedures is optional. The scope of a constant declared within a procedure is limited to the procedure in which it is defined. See Section 4.9.5.3 for more information on the CONSTANT declaration.

Syntax

CONSTANT constant-name := compile-time-constant-expression [[,...]];

4.9.4.9 ON_ERROR Statements

The use of ON_ERROR statements in procedures is optional. If you use an ON_ ERROR statement, you must place it at the top of the procedure just after any LOCAL and CONSTANT declarations. The ON_ERROR statement specifies the action or actions to be taken if an ERROR or WARNING status is returned. See Section 4.9.4.14 for more information on ON_ERROR statements.

Lexical Elements of the DEC Text Processing Utility Language 4–19