End node
The end node is simply the last command node in
a
command
STRING.
Example
:
':VOLT..
.
.
.'
end node is 'VOLT'.
':VOLT:AMPL..
. .
.'
end node is 'AMPL'.
Implied root node
The implied root node is a theoretical, unnamed and not really
existent command node, that prepends all root-level command nodes
of a given SCPI language.
Example
:
the partial command ref.
[:IMMediate] <event
>
:CONTinuous <boolean>
:AB
ORt <event
>
can be equated to:
<root
>
:INITiate
Remember
The <root> node does not really exist. Do not try programming
strings such as ":ROOT:INIT"
Current base node
The current base node is a virtual node like the <root> node. It is
a role that many nodes can play temporarily during the process of
parsing.
The current base node is not in the language definition, it is in the
parser. It is the node from where the parser starts when it tries to
match an incoming command string against the language definition.
How
the parser works
In this section we deal with the parsing of program messages and
program message units (commands) only.
Parameters (numbers, suffixes, enumerated values) have to be parsed
too of course, but this is quite straightforward and is not discussed
here.
The base operation of the parser is quite simple
:
Accept input characters until a node is gathered (until
':')
check the gathered node is below the current base node,
skip optional nodes if necessary.
5-4
Command Reference
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