TACL Reference Manual

Lexical Elements
HP NonStop TACL Reference Manual—429513-018
2-10
Comments
preserving the former value. For more information about variables and variable levels,
see Section 4, Variables.
Comments
TACL supports three forms of comments:
•
The “double equal” metacharacter: == comment text
This form causes TACL to ignore all subsequent text until the end of the line,
including braces and square brackets but excluding ampersands. To continue the
comment on the next line, use the line continuation character (&).
== this is a valid comment
== and this == is }{ a valid ][ comment
== this is a valid comment that &
is carried over to the next line }
•
Pairs of braces: { comment text }
When TACL encounters an opening brace, it ignores all subsequent text, including
double equal signs (==) and square brackets, until it encounters a closing brace.
The closing brace must appear on the same line unless you continue the line with
the line continuation character (&). An opening brace appearing within the
comment text is considered an error.
#OUTPUT This is not{this is a valid comment} a comment
{ this is a valid comment that &
is carried over to the next line }
{ this is an invalid comment; it exceeds one
line but has no "&" continuation character }
{ this is an invalid comment; it has two opening {'s }
•
The COMMENT command: COMMENT comment text
COMMENT is a TACL command that simply ignores its argument unless the
argument contains square brackets or braces. COMMENT is provided for
compatibility with earlier command interpreters; for new work, the use of braces or
double equal signs is recommended because of these special considerations:
°
If the argument contains a square-bracketed function, TACL executes the
function, but ignores its result along with the rest of the argument. A single left
bracket in the argument is not actually invalid, but causes unpredictable
results: TACL assumes it is the beginning of a function invocation and
Note. TACL does not prevent you from redefining TACL commands. You can, for example,
define a macro or function with the name TIME-a standard TACL command. You can also load
a segment file that has the same name as a TACL command. If you make such a change,
TACL will not act in its standard manner; it will, instead, execute your code.