Re: Advice on selling Ada to a C shop

[David Thompson <dave.thompson2@verizon.net>]

On Tue, 22 Jun 2010 22:39:51 -0700, Dennis Lee Bieber
<wlfraed@ix.netcom.com> wrote:

> On Tue, 22 Jun 2010 18:01:50 +0000 (UTC), anon@anon.org declaimed the
> following in comp.lang.ada:
> 
> > A second problem is until Ada 2012, C is the only common used language 
> > that allows functions to have "in out" type of parameters. If functions 
> > having the "in out" parameters, was a good idea, you would think then 
> > other older languages like Fortran, Pascal would have them.  Or even 
> 
> 	Uhm... The last time I worked FORTRAN (about a decade ago),
> functions COULD have side-effects. After all, the normal passing method
> in FORTRAN is by-reference, and I never encountered a compiler that
> would enforce read-only access to arguments inside a function. Now,
> maybe post '90/'95 standard have implemented such -- but I'd bet most
> shops are still running a compatibility option for older code...

Indeed. Classic Fortran did, and F90+ still does by default (i.e.
INTENT unspecified) or if you specify INTENT OUTor INOUT.
Only if you explicitly make a subprogram PURE or ELEMENTAL then a
function, but not a subroutine, is prohibited from having modifiable
arguments. (Both a function and subroutine are prohibited from other
'global' side-effects, i.e. on module~package data or external files.)

So did Pascal if you specify VAR, a68 with ref, and COBOL and PL/I
always. anon may argue that some of those are not now 'common[ly]
used', but Java certainly is and makes all nonprimitive arguments
writable references; there's not even a syntax to make a reference
readonly -- although you can write a target object, or a wrapper or
adapter etc., to be readonly (always or controllably) and some
important standard objects like java.lang.String are immutable.

And C++ of course, but that's arguably covered under C. It does have
added syntax for references (and OO 'this') but same semantics.