Re: Ada 2012: In-out parameters for functions

["Peter C. Chapin" <PChapin@vtc.vsc.edu>]

On 05/01/2013 12:28 PM, dptrash@arcor.de wrote:

> Why does Ada 2012 have in-out parameters for functions?
>
> Quote from the book 'Ada 2005 Rationale' (page 4): "[..] Indeed many other changes were rejected as really unnecessary. These include old chestnuts such as in out and out parameters for functions (ugh), [..]".

Section 4.2 of the Ada 2012 Rationale addresses this question. One 
particularly interesting sentence is: "The big concern was that allowing 
parameters of all modes might open the door to dangerous programming 
practices but a solution to that was found in the introduction of 
stricter rules preventing many order dependences."

Even in Ada 2005 it was permitted to pass access types to functions, 
effectively allowing a function to modify its parameter (via the access 
value). So in that respect not much has changed except that access types 
are no longer needed in yet another place in Ada.

Peter