Eliran Gonen <[EMAIL PROTECTED]> writes:
> It was just an example. Generally, interpreted languages are doing quite
> a good job when it comes to portability.
This statement is made so often (also about Java, which is not
interpreted, but I'll take some artistic license here and lump it all
together), that I think it is worth pausing for a second and thinking
about what it means.
The actual implementation (such as JVM or python itself etc) that is
necessary to run your program written in such a language is normally
written in a language like C. Someone has taken great care to
guarantee (bugs notwithstanding) that whatever you write in Java or
Python will be portable *across all the platforms that the core
implementation works on*.
So "portable" in the Java/Python/etc sense means *portable across a
limited, albeit maybe wide enough, range of platforms*. This is a very
different notion of portability than that of, say, ISO C. Since a JVM
is just a particular C program your Java application will be
necessarily no more portable than an ISO C equivalent[1][2]. "No more"
means, of course, "less or equally". Equality can only be attained if
the JVM is written in strict ISO C *and* all your target platforms can
accomodate both JVM (or Python, or whatever) and your applications in
terms of resources and facilities.
>From here you can easily come to the conclusion that there may be lots
of cases where to write portably you cannot use Java or Python or Ruby
or whatnot. It simply depends on what you mean by "portable", and what
your needs are.
I am not trying to argue that Python or Java are deficient in any
way. I am only pointing out the fact that when blanket statements like
"You want to write portably, write in Java" are made, it is worth
thinking of what it actually means.
[1] One can say that the advantage of Java for the programmer lies in
the lack of a superset of the spec that includes implementation
dependent and other non-standard stuff, so the programmer does not
have to think, "is this statement portable?" all the time. This is
true, but only to the point when you recall our favourite
company's "embrace and extend" philosophy that makes them so good
at introducing incompatibilities in everything. I don't really
follow, but didn't they win their latest round agaist Sun as far
as Java compatibility is concerned?
[2] Another great strength of Java and python etc is that there is a
minimal set of functionality that every compliant implementation
has to support, so you are at little risk of writing something
that will not be supported. This is in contrast to, say, C++ where
it is amazingly easy to write something perfectly standard that
will not be supported on some important platform (that will remain
unnamed). I don't know if there is an "embrace and truncate"
philosophy or plans thereof in any quarters, but we may all live
to see that day as well.
--
Oleg Goldshmidt | [EMAIL PROTECTED]
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