ConvertBot: Covers the NeXtMidas macro language syntax.

2020-04-27T18:39:27Z

Covers the NeXtMidas macro language syntax.

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'''Summary:''' Covers the NeXtMidas macro language syntax.
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Macros are scripts written in the Midas language. They are usually interpreted
languages that may or may not have a translation step. In X-Midas, macros have
a text (.txt) and binary (.mcr) form. In NeXtMidas, only the text (.mm) form
is used.

=== Translation - the just-in-time translator<span id="Translation"></span> ===

NeXtMidas macros employ a just-in-time translator. Labels, procedures, and
subroutines, are resolved at load time. Each command line is parsed into
an args table and the command object is loaded the first time the command
is run. Subsequent passes through the code have minimal overhead. Control
flow is implemented in the corresponding Intrinsic command using jumps
evaluated during translation.

Unlike X-Midas there are no .TXT or .MCR files. A NeXtMidas macro has the
extension .MM for Midas Macro. Since it is translated on-the-fly, there
are no translated files (.MCR) on disk. The extension is changed to allow
backward support of X-Midas macros.

=== Setup - Graphical setup files<span id="Setup"></span> ===

The graphical (.SET) files of X-Midas are replaced with (.MMP) for Midas
Macro Properties. This file holds graphical as well as non-graphical tuning
parameters that are undesirable in the macro text for clarity and re-use
reasons. For example, a macro that can be run locally, remotely, or in a
browser may have significantly different graphical setups. This can be
handled in separate .MMP files instead of multiple if-then-else statements
within the macro.

=== Structure - the basic structure of a NeXtMidas macro<span id="Structure"></span> ===

The basic structure is shown below:

startmacro a:arg1[default1] n:arg2[123]
local res1 res2 res3
global appstate
command1 in=arg1 out=_cb1
command2 in=_cb1 out=_cb2
endmacro

procedure open
return

procedure process
return

procedure processMessage m:msg
return

procedure processException m:emsg
return

procedure close
return

procedure proc1 s:file=default d:mode
return

procedure proc2
return

subroutine sub1 s:file=default d:mode
return

The first line defines the results names that will contain the parameters
supplied at run-time or by the defaults in the command configuration.

By default, all results created by a macro have local scope only. They are
not accessible by other macros and are automatically destroyed at macro
completion. Global results are always available for read access. To
make a global results writable by a macro, it must be called out using the
GLOBAL statement. The LOCAL command is optional, but can be used with the
GLOBAL and IMPLICIT statements to enforce strong type checking.

The open, process, processMessage, and close procedures apply only to
piped macros.

Control flow and argument parsing overhead for a 3 arg command in a
NeXtMidas macro measures approximately 35uSec on a 266MHz laptop.

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ConvertBot: Covers the NeXtMidas macro language syntax.