greg wrote:
If you're going to indulge in argument by authority,
you need to pick authorities that can be considered,
er, authoritative in the field concerned...
Like Barbara Liskov, who's won tons of awards for her work on computer
science and programming languages, and who was among the first to
design, implement, and formally describe a language with *exactly* the
same evaluation semantics as Python? What did she and her co-authors
have to say about the calling semantics in their new language? Let's see:
"In particular it is not call by value because mutations
of arguments performed by the called routine will be
visible to the caller. And it is not call by reference
because access is not given to the variables of the
caller, but merely to certain objects."
Let's take that again, with emphasis:
"IN PARTICULAR IT IS NOT CALL BY VALUE because mutations
of arguments performed by the called routine will be visible to
the caller. And IT IS NOT CALL BY REFERENCE because access
is not given to the variables of the caller, but merely to
certain objects."
"It is not". "And it is not".
But maybe they were just ignorant, and didn't really "get" how earlier
languages worked? Let's see what Liskov has to say about that:
"The group as a whole was quite knowledgeable about languages that
existed at the time. I had used Lisp extensively and had also
programmed in Fortran and Algol 60, Steve Zilles and Craig
Schaffert had worked on PL/I compilers, and Alan Snyder had done
extensive programming in C. In addition, we were familiar with
Algol 68, EL/1, Simula 67, Pascal, SETL, and various machine
languages. Early in the design process we did a study of other
languages to see whether we should use one of them as a basis for
our work [Aiello, 1974]. We ultimately decided that none would be
suitable as a basis. None of them supported data abstraction, and
we wanted to see where that idea would lead us without having to
worry about how it might interact with pre-existing
features. However, we did borrow from existing languages. Our
semantic model is largely borrowed from Lisp; our syntax is
Algol-like."
Still think they didn't understand Algol's semantic model?
:::
But nevermind - the real WTF with threads like this one is the whole
idea that there are two and only two evaluation strategies to choose
from. That's a remarkable narrow-mindedness.
</F>
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