TACL Reference Manual

HP NonStop TACL Reference Manual—429513-018
4-1
4 Variables
In many other languages, the term variable refers to a simple variable that contains a
single element, such as the number 10, or a more complex variable that contains an
set of elements. In TACL, a variable can contain a single element, a set of elements, or
information as diverse as a hierarchy of variables or a series of TACL statements.
You can create, set, and delete variables. You can access variables interactively or
load them into memory from a file. For more information about loading variables, see
Section 5, Statements and Programs.
This subsection provides general information about variables, including a discussion of
the stack organization of variables. The remainder of this section provides information
about each type of TACL variable.
Along with the variables you create, TACL supplies a set of variables. These variables
are called built-in variables and are listed in Section 9, Built-In Functions and
Variables.
An Overview of TACL Variables
A TACL variable can contain data, TACL statements, or other information. Table 4-1
lists the seven types of variables. TEXT variables can be used to contain text or
procedural constructs.
Table 4-1. TACL Variables and Their Uses (page 1 of 2)
Variable
Type Description
TEXT Contains text or a sequence of TACL statements. A text variable that
contains text is most similar to simple variables used by other programming
languages. A TEXT variable that contains TACL statements does not
accept arguments, but can be used in a similar way as a MACRO variable
(described below) if arguments are not necessary.
ALIAS Contains the name of a TACL variable. An ALIAS variable allows you to
invoke a variable by a different name: the alias name. Any arguments
supplied when invoking an alias variable are passed to the referenced
function.
MACRO Contains a sequence of TACL statements. Arguments presented to the
macro are substituted, without interpretation or checking, for dummy
arguments in the macro text; each argument is referenced by position.
ROUTINE Contains a sequence of TACL statements. A routine can parse its own
arguments (TACL supports several predefined argument types) and can
compute its own result.