Re: [MI400] RE: MI emulator

[Simon Coulter <shc@xxxxxxxxxxxxxxxxx>]

On Saturday, October 11, 2003, at 05:09  AM, Jon Paris wrote:

> I must admit I find the fascination with MI hard to understand.  We all
> "own" the C compiler now (C++ too for that matter) - the majority of 
> the
> useful MI functions are surfaced in the C library and in many cases 
> will
> outperform the "native" (not that there is such a thing) MI anyway.
>
> Just what is it that can be done so much better in MI that makes it 
> worth
> dealing with the absence of tools, documentation, syntax checkers, 
> debuggers

It is not so much a case of 'better' but rather there is no other way 
to do some things. The C interface to MI is somewhat sanitised. There 
are some things that simply cannot be done without resorting to MI. 
Even things as innocuous as creating a hidden temporary space or index 
cannot be done except via MI. There aren't many business applications 
that need MI but for systems stuff it is sometimes necessary.

There is a debugger. It's called STRDBG. It may not have source debug 
capability (but that's another of my little projects) but it is 
certainly possible to debug MI programs the same way we used to debug 
CL and RPG programs. The AS/400 MI Functional Reference is readily 
available and that in conjunction with the S/38 MI Functional Reference 
is all that is needed. A copy of the S/38 Functional Concepts manual is 
also helpful as is a copy of the multi-volume S/38 Data Areas 
reference. The S/38 CPF micro-fiche is useful too. Syntax checking is 
not such a big deal because the MI syntax is quite simple and 
consistent.

Some things require system state (like inserting a hidden space into a 
context) and although anyone with access to SST can patch a program 
into system state it is harder to do that in such a way as to allow the 
resulting object to be restored to another system. Doing that to an OPM 
program is easier than to an ILE program.

Regards,
Simon Coulter.
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