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Posted by Alf P. Steinbach on 10/07/07 10:10
* James Kanze:
> On Oct 4, 12:35 am, "John W. Kennedy" <jwke...@attglobal.net> wrote:
>> Dennis Lee Bieber wrote:
>>> On Mon, 01 Oct 2007 01:53:47 GMT, Roedy Green
>>> <see_webs...@mindprod.com.invalid> declaimed the following in
>>> comp.lang.python:
>
>>>> Seem to me you could in FORTRAN and Pascal, and maybe even Algol. It
>>>> has been a while.
>
>>> Everything in classic FORTRAN is a passed as a reference -- even
>>> constant arguments are passed as a reference to the memory location
>>> containing that constant (which is why it was possible in very early
>>> FORTRANs to have "a = 1 + 1" yield something other than "2" if preceded
>>> by, say, "call mutate(1)" where mutate looks like:
>
>>> subroutine mutate(arg)
>>> arg = arg * 2
>>> end
>>> )
>
>> However, some implementations passed /and returned/ elementary
>> arguments by value, as Ada does. (The object code was
>> typically faster that way, and FORTRAN semantics were such
>> that the difference was almost impossible to observe.)
>
> The Fortran standard is carefully worded to allow either pass by
> reference, or copy-in, copy-out. IIRC, IBM's Fortran-H used
> copy-in/copy-out, but most others used call by reference.
>
> Straight copy was never allowed by the standard, and I've never
> heard of a pre-standard implementation which used it either.
This is all to simple. Please discuss Algol pass-by-name. Much more
interesting, and a good candidate for inclusion in C++ -- at least, if
we're going to achieve the goal of PL/1-killer! :-)
Cheers,
- Alf (off-topic)
--
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