TACL Reference Manual

Built-In Functions and Variables
HP NonStop TACL Reference Manual—429513-018
9-113
#DELTA Built-In Function
Comments
Comments help to produce readable #DELTA code. A #DELTA comment is an
exclamation point (!) followed, optionally, by explanatory text to the end of the line. You
can also use the standard TACL “{ }” and “==” comments within #DELTA. (Using TACL
comments could be safer because #DELTA ignores all text within comments; you can
also continue them over additional lines by using ampersands. However, #DELTA
parses “!” comments, so errors within those comments are possible.)
The Buffer
The main work area in #DELTA is a buffer that can contain up to 30,000 characters.
However, there could be fewer than 30,000 characters available because of ongoing
TACL activity. (At the time #DELTA exits, not more than 15,000 characters can remain
in the buffer or a “Text buffer overflow” error occurs.) Use the HT command to display
the contents of the buffer; for example:
10> [#DELTA These characters are the
10> contents of the buffer]
#DELTA 11> HT
#DELTA 11> EOF!
These characters are the
contents of the buffer
#DELTA provides ways of moving all or part of the buffer to or from files or variable
levels. All editing is done on the text in the buffer.
#DELTA does no character translation during file I/O or while accessing variable levels;
all data access is done in the PLAIN mode. For example, when #DELTA reads a file,
square brackets and vertical bars remain ordinary text; they do not become TACL
invocation characters. Comments are not eliminated, nor do ampersands function as
continuation characters.
When #DELTA reads a variable level containing a routine or a macro, special internal
character sequences appear in the buffer. In particular, a square bracket or vertical bar
appears as a pair of bytes, the second of which is the square bracket or vertical bar
(the first is RVU-dependent and subject to change); remember this point when
counting characters.
The Pointer
The pointer indicates your current position in the buffer. Some commands use the
pointer value; others modify the position of the pointer. The #DELTA pointer points
between characters. When you use a command that depends on the pointer value,
#DELTA operates on the characters relative to the pointer position.
You can display the current pointer value by entering a period followed by an equal
sign (.=). The V (view) command shows lines in the buffer and indicates by (.) the
position of the pointer within the buffer; for example:
14> #DELTA Test string
#DELTA 15> .=