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Date: Sat, 30 Apr 2022 04:30:14 -0700 (PDT)
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Subject: Re: Question on in/out parameters
From: reinert <reinkor@gmail.com>
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Thanks for sorting out my confusion.=20

So there is no difference between "in", "in out" and "out" for Vectors exce=
pt that the compiler protests if I try to change an "in parameter" in the a=
ctual subroutine/function?

reinert


l=C3=B8rdag 30. april 2022 kl. 11:38:08 UTC+2 skrev Jeffrey R.Carter:
> On 2022-04-30 10:57, reinert wrote:=20
> >=20
> > I expected an "out" parameter in a procedure to be like declaring the p=
arameter "from scratch" (with actual initial default value). For my compile=
r (GNAT Community Edition, May 2021) it seems like the out parameters bring=
s in content from the calling procedure. Should it be like this?
> Parameters in Ada are either passed by copy or passed by reference, regar=
dless=20
> of parameter mode. The rules are=20
>=20
> * Scalar types are always passed by copy=20
> * Tagged types are always passed by reference=20
> * Limited types are always passed by reference=20
> * All other types are decided by the compiler=20
>=20
> For the types that are passed by reference, "in out" and "out" mode are i=
dentical.=20
>=20
> Vector is a tagged type, so this applies to it.=20
>=20
> One can argue that an out-mode parameter of a by-reference type should be=
=20
> "reinitialized" before use, but the Ada-9X revision decided not to requir=
e this.=20
>=20
> --=20
> Jeff Carter=20
> "Hello! Smelly English K...niggets."=20
> Monty Python & the Holy Grail=20
> 08