Re: Would an *AdaScript* language be a good / bad idea?

[Darren New <dnew@san.rr.com>]

Stephen Leake wrote:
> Perhaps there is a better term for this than "scripting language". For
> example, Java has this capability, and it is _not_ a "scripting
> language" by your definition (at least, I don't think it is :). Lisp
> has this feature; is that a "scripting language"?

I don't think "scripting language" is sufficiently precise a term that you
can draw a circle that encompasses all and only scripting languages. I don't
think there's any one feature that defines what is and is not a scripting
language. Clearly, Ada is not. Clearly, /bin/bash is. Lisp and Java probably
fall in the middle somewhere. I was just saying that the glue orientation,
the dynamic code loading, and a few other features are generally usually
found in scripting languages and usually not in non-scripting languages. The
idea of "adascript" being just like Ada only without the type declarations
or just like Ada only interpreted wouldn't necessarily be a scripting
language.

My point was that I don't think an AdaScript that's the same as Ada only
without any type declarations makes sense. If you managed to make it make
sense, it wouldn't be useful, because people don't use scripting languages
solely because of weak typing. (And many languages that could arguably be
called scripting languages or close to it are strongly typed, such as Java,
Python, Smalltalk, etc.) The point of having the weak typing is to (a) make
the source smaller so it loads faster over the net, and (b) to build in all
kinds of things that don't make sense in a general-purpose language.
Consider elisp's access to buffers and such, and javascript's access to the
current web page, and etc.

If you want to consider "AdaScript", I'd suggest first ask "what would I add
to make it attractive as a scripting language", rather than asking "what
need I take away from Ada."  Once you decide what features you want to add,
you can ask what features of Ada make those new features unusually difficult
to implement.

> > If it can, that would be really cool, because it would solve a
> > problem I've been thinking about for a while in an unrelated field.
> > But I haven't figured out any way of doing that without knowing what
> > part of the program constitutes the "current state".
> 
> I gather you want the "save the state" operation to be provided by the
> compiler, not by the programmer. I guess that is true in the languages
> that have "dynamic code loading".

No. The state doesn't get saved in that case, because you're not starting a
new program. You're just adding new code to the current program. You don't
need to "save the state" of a program loading new code in Tcl or Java any
more than you need to 'save the state" of a program before loading a DLL in
Windows or before opening a data file in Ada.

> Although the distributed annex
> comes close; you could change out a partition without restarting the
> other partitions.

I'm curious how you would do this. Is it actually possible to do this within
the language, or would one have to (for example, in GNAT) sigkill the
process running the part you want to change or something? In other words,
from my very limited understanding, it seems like the distributed annex is
more about distribution and less about dynamic interconnection. I may have
just not played with it enough to get the "aha" there.

-- 
Darren New 
San Diego, CA, USA (PST). Cryptokeys on demand.
** http://home.san.rr.com/dnew/DNResume.html **
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     My brain needs a "back" button so I can
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