[OT] Strong/Weak/Dynamic/Static typing (was Re: Python Strings)
m.faassen at vet.uu.nl
Mon Sep 25 15:41:26 CEST 2000
Jonadab the Unsightly One <jonadab at bright.net> wrote:
> m.faassen at vet.uu.nl (Martijn Faassen) wrote:
[snip me trying to comprehend inform and detailed answers]
>> What Inform seems to do is expose some implementation details (addresses),
>> though I'm not quite sure how it could work internally yet..
> Actually, they're not really exposed to the casual programmer;
> the Designer's Manual doesn't talk about them really. I know
> about them because I've read the technical manual and the
> specification of the z-machine and no small number of related
> technical discussions on rec.arts.int-fiction.
Ah, I see, Inform is a language for interactive fiction! Interesting..
> As far as the
> casual programmer is aware, you can simply do something like
> the code below.
> Notice that the description property of one
> object holds a string, and the description property of the
> very next object holds a routine (which executes a rather
> lousy joke I shamelessly ripped off from Graham Nelson for
> the sake of the example, but nevermind). When the library
> is ready to print the description of the first object, it
> discovers a string and just prints it. When it is ready
> to print a description of the second object, it discovers
> a routine and runs it.
Right, in Python you could do the same (by overloading __str__() for
In LPC (which is yet another C derived interpreted object oriented language
used in lpmuds (more interactive function) since the early 90s or late 80s even
-- and they called Java innovative :), you have the concept of
'VBFC', which I believe stands for Variable By Function Call. You do
much the same thing with it; instead of having a string you can put a function
call in its place, even interpolated, I believe.
> Since the routine returns true
> rather than false (which would be the default) it assumes
> that the routine has printed something. If the routine
> had not returned true, the library would have printed
> a default "You see nothing special about the spade."
Again similar to LPC, where if a function (method really) returns 1, the
attempt at parsing the command the player typed is taken to have succeeded.
You can optionally define a failure message in case true is not returned.
I wonder if Inform's evolution of this was independent or somehow related
to LPC? It may be a general pattern in languages like this. And though
both languages are object oriented, both don't seem
to use the normal OO techniques to accomplish this effect.. Interesting!
> And here's an example of substituting a routine for an object...
[snip another example]
Yes, the solution in LPC to that problem (an exit with special behavior)
is quite similar.
[snip stuff about the z-machine; I recall reading about this]
>  MUCH more portability than Python, but of
> course it has a cost in power.
Does Inform code compile to the average z-machine? I recall that lots of
z-machines have rather strict limitations on how much memory objects
> There is also
> now a newer VM (glulx) which kicks out all the
> size limitations a few orders of magnitude
> and supports sound and graphics and I think
> limited file I/O; it will still be more portable
> and less powerful than Perl or Python.
Does glulx still port to the old machines you mentioned too, though?
If not then Python may not be much less portable.
>  The low addresses (which are not packed) are
> RAM, and the packed addresses are ROM.
> So all strings and routines are in ROM, but
> all objects reside in RAM.
You can't put them in physical ROM though. I presume you mean that strings and
routines are in (to the z machine) immutable memory. Do they use the term
ROM for this?
[types in Inform are partially distinguished by address range]
> It's a kludge, but it works, and
> it lets the compiler, library, and indeed the
> program see distinctions that apparently the
> VM was not designed to see.
I wonder why Inform didn't take the approach of putting the distinctions
within the object, instead of in the references (like Python does).
>  I know these footnotes don't appear in order.
> I didn't write the post in order. I usually
> don't write straight from beginning to end.
> Besides, there is no footnote 9.
Thanks for all the interesting information. I should check out Inform and
z-machine, if only perhaps to steal ideas. :)
History of the 20th Century: WW1, WW2, WW3?
No, WWW -- Could we be going in the right direction?
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