TACL Reference Manual

Variables
HP NonStop TACL Reference Manual—429513-018
4-4
Specifying a Level of a Variable
The choice of a declaration mechanism depends on whether you want to define the
variable interactively, within a file, or in a library. For more information about files and
libraries, see Section 5, Statements and Programs.
When you create a variable, TACL creates level 1 of the variable. To create additional
levels, push or define the same variable. TACL then creates a new level of the variable
and increments the level number.
You can use the #FRAME built-in function at the start of a macro or routine to define a
local environment for variables. If you create variables within a frame, you can remove
all the variables and their levels by deleting the frame with an #UNFRAME or #RESET
FRAMES operation.
A variable remains in existence unless you delete it with a #POP function call, POP
command, an #UNFRAME operation, or a #RESET FRAMES operation.
Specifying a Level of a Variable
To specify a level of a variable, append a period and a level number to its name. If you
omit the level number, TACL accesses the top level.
You can specify a level number in one of two ways:
•
Numbers greater than zero refer to levels relative to the bottom of the stack; they
indicate the order of creation of the levels. As an example, name.1 is the bottom
level, name.2 is the next to the bottom level, and so on.
•
Numbers less than or equal to zero refer to levels relative to the top of the stack;
they indicate how far down a level is from the top of the stack. Therefore, name.0
is the top level, name.-1 is the next to the top level, and so on.
This diagram shows the two ways to address levels of the sample variable var1:
Different levels can contain different types of data. For example, the first level of a
variable could contain an alias, the second level could contain text, and the third level
could contain a macro.
Bottom-Up Addressing Top-Down Addressing
var1.3 (top), also accessible as var1 XYZ var1.0
var1.2 A var1.-1
var1.1 35 var1.-2