MIDAS Command Language

The MIDAS command language ( MCL) 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 procedures.
The MCL 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 20 levels deep).

MIDAS procedures  are handled in the following way:
The ASCII procedure file is read in by the MIDAS monitor  and translated into an internal more compact format. This translated code is then executed inside the Monitor.
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 GOTO 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.

For a detailed explanation of all the MIDAS Command Language commands see the appendix of this volume or use the MIDAS command HELP/CL.

The following Command Language commands provide the necessary programming constructs like looping and conditional branching for MIDAS procedures, they cannot be used interactively:

BRANCH variable comparisons labels
Compare variable with comparison values and branch to related labels

CROSSREF label1 ... label8
Define cross reference labels for parameters par1 ... par8

DEFINE/LOCAL key data all_flag level_flag
Define local keyword key and initialize it using data

DEFINE/PARAMETER par def type prompt limits
Declare default value, type, promptstring and limits for parameter par

DO loopvar = begin end step_size
... command body...
ENDDO
Execute a do--loop (as in FORTRAN)

ENTRY procedure
Define the beginning of a MIDAS procedure in procedure file with a different name

GOTO label
Jump to a label defined as label:, see below

IF par1 op par2 command
Execute conditional statement (as in FORTRAN)

IF par1 op par2 THEN
... if-sequence...
ELSEIF par1 op par2 THEN
... else if-sequence...
ELSE
... else-sequence...
ENDIF
Execute a conditional statement (as in FORTRAN)

INQUIRE/KEYWORD key prompt-string
Demand value for key from the user

label:
Declare a label,e.g. HOME:

RETURN par1 ... par3
Return to calling procedure or terminal and pass up to 3 parameters

PAUSE
interrupt the current procedure and return to interactive level

DEFINE/MAXPAR nopar
Indicate that max. nopar parameters are expected


The following commands may also be used interactively, but are especially useful inside MIDAS procedures:

@ (or: @@, or: @a, or: @s, or: @c proc par1 ... par8)
Execute the MIDAS procedure proc which is stored
in MID_PROC:, (or in the current directory or MID_WORK:),
or in APP_PROC:, or in STD_PROC:, or in CON_PROC:, respectively

ECHO/qualif levela,levelb
Control the display of MIDAS commands ( qualif = ON, OFF, FULL)
for procedures executing at a level in the interval [ levela,levelb]

COMPUTE/KEYWORD reskey = expression
Evaluate an algebraic expression involving keywordss and constants, store result in reskey

SET/FORMAT I-format E-format
Define formats used for replacements of keyword and descriptor names
in procedures with their actual values

WRITE/OUT text
Display text on terminal

! comment
Indicate beginning of a comment line

Note is good practice not to abbreviate the commands  and qualifiers  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.
The command TRANSLATE/SHOW myproc X will check that all commands and qualifiers are fully specified in procedure myproc.prg.

• Passing Parameters in MIDAS Procedures
• Symbol Substitution in Command Procedures
• DO Loops
• Local Keywords
• Conditional Statements, Branching
• Special Functions
• Interrupting Procedures
• Entry points