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<H1><A NAME="SECTION00660000000000000000"> </A><A NAME="1809"> </A>
<A NAME="midas-command-language"> </A>
<BR>
MIDAS Command Language
</H1>
<P>
The MIDAS command language (<TT>MCL</TT>)
consists of all the commands which you enter
interactively, and an additional set of commands to provide the necessary tools
to write MIDAS ``programs'', called MIDAS <I>procedures</I>.
<BR>
The <TT>MCL</TT> is a flexible and powerful tool to integrate
application modules into MIDAS and to do rapid prototyping. But it is not
intended to be a
full blown programming language - for programming tasks MIDAS supports the
standard interfaces in FORTRAN 77 and C (cf. the MIDAS Environment document).
It is an interpreted language, so you do not need
to compile MIDAS procedures. It is also a ``Macro'' language in the sense that
you can build complex procedures, attach these procedures to a MIDAS command
and qualifier combination and then put a single line with that command name
into yet another procedure (up to 25 levels deep).
<BR>
<BR>
MIDAS procedures<A NAME="1814"> </A> are handled in the following way:
<BR>
The ASCII procedure file is read in by the MIDAS monitor<A NAME="1815"> </A> and translated into
an internal more compact format. This translated code is then executed inside
the Monitor.
<BR>
The individual lines of code are parsed and decoded in two
passes: In the first pass, all symbol substitutions are done using the specified
formats to convert from binary to ASCII. In the second pass,
all control and conditional
statements are processed directly by the Monitor (e.g. positioning the internal
program pointer to the command line referred to by a <TT>GOTO</TT> statement)
until
an ``executable'' command line is found which is passed on to the usual
command input pipeline of MIDAS as if it were typed in by the user.
<BR>
<BR>
For a detailed explanation of all the MIDAS Command Language commands see
the appendix of this volume or use the MIDAS command <TT>HELP/CL</TT>. <BR>
<BR>
The following <I>Command Language</I> commands provide the necessary programming
constructs like looping and conditional branching for MIDAS procedures, they
cannot be used interactively:
<BR>
<BR>
<TT>BRANCH variable comparisons labels</TT>
<BR>
Compare <I>variable</I> with <I>comparison</I>
values and branch to related <I>labels</I> <BR>
<BR>
<TT>CROSSREF label1 ... label8 </TT>
<BR>
Define cross reference <I>labels</I> for
parameters par1 ... par8 <BR>
<BR>
<TT>DEFINE/LOCAL key data all_flag level_flag</TT>
<BR>
Define local keyword <I>key</I> and initialize it using <I>data</I> <BR>
<BR>
<TT>DEFINE/PARAMETER par def type prompt limits</TT>
<BR>
Declare <I>default</I> value, <I>type</I>,
<I>prompt</I>string and <I>limits</I> for parameter <I>par</I> <BR>
<BR>
<TT>DO loopvar = begin end step_size</TT>
<BR>
<TT>...command body...</TT>
<BR>
<TT>ENDDO</TT>
<BR>
Execute a do-loop (as in FORTRAN) <BR>
<BR>
<TT>ENTRY procedure</TT>
<BR>
Define the beginning of a MIDAS <I>procedure</I>
in procedure file with a different name <BR>
<BR>
<TT>GOTO label</TT>
<BR>
Jump to a <I>label</I> defined as <I>label:</I>, see below <BR>
<BR>
<TT>IF par1 op par2 command</TT>
<BR>
Execute conditional statement (as in FORTRAN)
<BR>
<BR>
<TT>IF par1 op par2 THEN</TT>
<BR>
<TT>...if-sequence...</TT>
<BR>
<TT>ELSEIF par1 op par2 THEN</TT>
<BR>
<TT>...else if-sequence...</TT>
<BR>
<TT>ELSE</TT>
<BR>
<TT>...else-sequence...</TT>
<BR>
<TT>ENDIF</TT>
<BR>
Execute a conditional statement (as in FORTRAN)
<BR>
<BR>
<TT>INQUIRE/KEYWORD key prompt-string </TT>
<BR>
Demand value for <I>key</I> from the user <BR>
<BR>
<TT>label:</TT>
<BR>
Declare a <I>label</I>, with <I>label</I> a string beginning with a letter, e.g. <TT>Step_A:</TT> <BR>
<BR>
<TT>RETURN par1 ... par3</TT>
<BR>
Return to calling procedure or terminal and
pass up to 3 parameters <BR>
<BR>
<TT>PAUSE </TT>
<BR>
interrupt the current procedure and return to interactive level
<BR>
<BR>
<TT>DEFINE/MAXPAR nopar </TT>
<BR>
Indicate that max. <I>nopar</I> parameters are expected <BR>
<BR>
<BR>
The following commands may also be used interactively, but are especially
useful inside MIDAS procedures:
<BR>
<BR>
<TT>@</TT> (or: <TT>@@</TT>, or: <TT>@a</TT>, or: <TT>@s</TT>, or:
<TT>@c proc par1 ... par8</TT>)
<BR>
Execute the MIDAS procedure <I>proc</I> which is stored
<BR>
in MID_PROC:, (or in one of the current procedure directories)
<BR>
or in APP_PROC:, or in STD_PROC:, or in CON_PROC:,
respectively
<BR><BLOCKQUOTE>
<DIV ALIGN="CENTER">
<B>Note</DIV>
<I>Up to 4 directories for procedures can be specified via the command
<TT>SET/MIDAS PATH=</TT>. By default the current directory and the directory
pointed to by the variable <TT>MID_WORK</TT> are used to localize Midas procedures
when using the <TT>@@</TT> command.</I></B></BLOCKQUOTE><TT>ECHO/qualif levela,levelb</TT>
<BR>
Control the display of MIDAS commands
(<I>qualif</I> = ON, OFF, FULL)
<BR>
for procedures executing at a level in the
interval [<I>levela,levelb</I>]
<BR>
<BR>
<TT>COMPUTE/KEYWORD reskey = expression</TT>
<BR>
Evaluate an algebraic <I>expression</I>
involving keywordss and constants, store result in <I>reskey</I> <BR>
<BR>
<TT>SET/FORMAT format_specs</TT>
<BR>
Define <I>format</I>s used for replacements
of keyword and descriptor names <BR>
in procedures with their actual values <BR>
<BR>
<TT>WRITE/OUT text</TT>
<BR>
Display <I>text</I> on terminal <BR>
<BR>
<TT>! comment</TT>
<BR>
Indicate beginning of a <I>comment</I> line
<BR><BLOCKQUOTE>
<DIV ALIGN="CENTER">
<B>Note</DIV>
<I>It is good practice NOT to abbreviate the commands<A NAME="1884"> </A> and qualifiers<A NAME="1885"> </A> of a
MIDAS command inside a procedure. Since new MIDAS commands can be created
any time an abbreviated command may work at one time but
become ambiguous at other times and cause the procedure
to fail.
<BR>
The command <TT>TRANSLATE/SHOW myproc X</TT> will check that all commands and
qualifiers are fully specified in procedure <TT>myproc.prg</TT>.
<BR>
<BR>
Also avoid relying on the defaults of parameters of a given command.
With the command <TT>CREATE/DEFAULT</TT>
these defaults can be changed dynamically. Instead write full command lines
specifying all parameters in your procedures.</I></B></BLOCKQUOTE>
<P>
<BR><HR>
<!--Table of Child-Links-->
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<UL>
<LI><A NAME="tex2html959"
HREF="node39.html">Passing Parameters in MIDAS Procedures</A>
<LI><A NAME="tex2html960"
HREF="node40.html">Symbol Substitution in Command Procedures</A>
<LI><A NAME="tex2html961"
HREF="node41.html">DO Loops</A>
<LI><A NAME="tex2html962"
HREF="node42.html">Local Keywords</A>
<LI><A NAME="tex2html963"
HREF="node43.html">Conditional Statements, Branching</A>
<LI><A NAME="tex2html964"
HREF="node44.html">Special Functions</A>
<LI><A NAME="tex2html965"
HREF="node45.html">Interrupting Procedures</A>
<LI><A NAME="tex2html966"
HREF="node46.html">Entry points</A>
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<ADDRESS>
<I>Petra Nass</I>
<BR><I>1999-06-09</I>
</ADDRESS>
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