On 11/07/2012 04:00 PM, Steven D'Aprano wrote:
Andrew, it appears that your posts are being eaten or rejected by my
ISP's news server, because they aren't showing up for me. Possibly a side-
effect of your dates being in the distant past?
Date has been corrected since two days ago. It will remain until a
reboot....
Ignorance, though, might be bliss...
Every now and again I come across somebody who tries to distinguish
between "call by foo" and "pass by foo", but nobody has been able to
explain the difference (if any) to me.
I think the "Call by foo" came into vogue around the time of C++; Eg:
It's in books like C++ for C programmers; I never saw it used before
then so I *really* don't know for sure...
I know "Pass by value" existed all the way back to the 1960's. I see
"pass by" in my professional books from those times and even most newer
ones; but I only find "Call by value" in popular programming books of
more recent times. (Just my experience) So -- I "guess" the reason is
that when invoking a subroutine, early hardware often had an assembler
mnemonic by the name "call".
See for example: Intelx86 hardware books from the 1970's;
Most early processors (like the MC6809E, and 8080) allow both direct and
indirect *references* to a function (C would call them function
pointers); So, occasionally early assembly programs comment things like:
"; dynamic VESA libraries are called by value in register D."; And they
meant that register D is storing a function call address from two or
more vesa cards. It had little to do with the function's parameters,
(which might be globals anyway) (It procedural dynamic binding!)
Today, I don't know for sure -- so I just don't use it.
"pass" indicates a parameter of the present call; but not the present
call itself.
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