anything like C++ references?
tim.one at comcast.net
Thu Jul 17 20:28:09 CEST 2003
>> Anyway, Algol and Fortran apparently (I didn't know this until today)
>> *always* used call-by-reference.
> Not true (about Fortran). I vaguely remember (about 1980) when IBM
> Fortran switched from one calling convention to another. I initially
> missed the one-line change in the manual update sheets. A working
> program started giving strange results until I finally figured out
> what was going on and then found the one line 'announcement'.
Yes, many Fortran implementations used call-by-value/result, and that's fine
by Fortran's rules. The primary difference lies in whether assigning to
formal argument X appeared to change the value of formal argument Y too,
while you were still in the subroutine with those formal arguments, when the
caller passed the same variable as actual argument in both the X and Y
positions. In CBR, changes are instantly visible via aliases; in CBVR,
they're not. The Fortran standard finessed this simply by declaring
programs which relied on either specific behavior to be non-conforming
Algol's history is a lot more complicated too, and, indeed, the infamous
"call by name" came out of what was probably a mistake in the Algol 60
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