Re: general-purpose vs domain-specific programming languages

Re: general-purpose vs domain-specific programming languages

[Marin David Condic, 561.796.8997, M/S 731-96]

gwinn@res.ray.com writes:
>
>The preface/introduction to the Perl manual gives the game away.  Perl is
>intentionally designed to allow the violation of the majority of the usual
>good-programming practices and restrictions, such as the strict type
>safety that Ada is so famous for.
>
<snip>

    Well that would explain where it would be difficult to implement
    Perl functionality in Ada and why it might not matter anyway. As
    you say, Perl aims for quick-and-dirty hacks and that is
    definitely not what Ada aims at.

    Still, I think there might be some value in looking at what Perl
    (or any other language) may provide which could be useful in an
    Ada implementation. The original complaint, as I recall, that
    Terry had was that there was no primitive for scanning a text file
    for a string and replacing it with another string. That would seem
    to be a useful bit of functionality to have in ones Ada bag of
    tricks. I've built dozens of "utility" packages which provide
    things like linked lists, command line interpreters, string
    manipulation primitives, realtime control utilities (digital
    filters, etc), math functions and lots of other things which are
    useful in building systems. Often these utilities mimic
    functionality which might just naturally exist in some other
    language. If there is some definable chunk of Perl functionality
    which could be utilized in building Ada programs, why not make a
    package to provide those services?

    In general, I prefer to avoid mixed language systems because of
    the cost of maintaining them. (You've got to license two or more
    compilers/development suites, keep the knowledge base around,
    worry about divergence and later incompatibilities, porting
    issues, etc.) There are certainly tasks that are performed better
    by different languages, but if I've got, say 95% of my system best
    served by Ada and 5% best served by Perl (or Forth, or Lisp...) I
    might find it to my advantage to go ahead and take the hit of
    developing the capability of doing that remaining 5% in Ada just
    to avoid having to drag around a second language and all the risks
    associated with that.

    So might there be some set of Perl primitives that could be
    duplicated in an Ada environment?

    MDC

Marin David Condic, Senior Computer Engineer     Voice:     561.796.8997
Pratt & Whitney GESP, M/S 731-95, P.O.B. 109600  Fax:       561.796.4669
West Palm Beach, FL, 33410-9600                  Internet:  CONDICMA@PWFL.COM
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Re: general-purpose vs domain-specific programming languages

[Nick Roberts]

I've often found there is much mileage in developing very simple
interpreters, which are written in Ada, but which provide a separate
environment and language for doing a very specific job.

The 'environment' is typically line-oriented interaction (about as simple
as it can get); sometimes 'batch' file capability needs to be added (also
very simple: just read a named text file instead of current input).

As long as the syntax is kept very simple (cf. the 'ed' of UNIX), the
interpreter is easy to maintain, yet provides the thing it most needs to:
convenience. It is likely to be less convenient to have to write and
compile an Ada program to do something that would be a one-liner for such
an interpreter.

The biggest drawback tends to be psychological: persuading people to learn
the new syntax. Programmers seem to have a pathological neophobia when it
comes to this sort of thing!

-- 

Nick Roberts
Croydon, UK

Proprietor, ThoughtWing Software; Independent Software Development
Consultant
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