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From: harrison@software.ORG (Tim Harrison)
Newsgroups: comp.lang.ada
Subject: Usage of OTHERS choice
Message-ID: <8803091724.AA02141@ajpo.sei.cmu.edu>
Date: 8 Mar 88 22:40:33 GMT
Sender: uucp@ucbvax.BERKELEY.EDU
Organization: The Internet
List-Id: <comp.lang.ada>

I have submitted the following code to two validated compilers.  The
designated line is rejected as illegal by one of the compilers.  Is the
OTHERS choice actually illegal?

----------------------------------------------------------------------
package BOOLEAN_DATA is

  type BOOLEAN_ARRAY is array (NATURAL range <>) of BOOLEAN;

  procedure INITIALIZE(OBJECT : in out BOOLEAN_ARRAY);

end BOOLEAN_DATA;
package body BOOLEAN_DATA is

  procedure INITIALIZE(OBJECT : in out BOOLEAN_ARRAY) is
  begin
    OBJECT := (others => FALSE); -- rejected by one compiler
  end INITIALIZE;

end BOOLEAN_DATA;
----------------------------------------------------------------------

The compiler that rejects the code gives "RM 4.3.2(5):  OTHERS illegal for
unconstrained array" as the reason for rejection.  Here is what I believe to
be the basis for the decision to reject the OTHERS choice in this example.

RM 4.3.2(4-5) states:

    ...An *others* choice is only allowed if the aggregate appears in one   (4)
    of the following contexts (which defined the applicable index
    constraint):

    (a) The aggregate is ... the expression that follows an assignment      (5)
        compound delimiter.  Moreover, the subtype of the corresponding
        ... object is a constrained array subtype.

What is the subtype of the object OBJECT?  Can someone provide me with a
citation that specifies the subtype of OBJECT?

I think that the following citations are relevant, but they don't state
the case clearly enough for me to believe that they are providing me with a
definition for the subtype of OBJECT.

RM 6.2(9):
   "...For a formal parameter of an unconstrained array type, the bounds
    are obtained from the actual parameter, and the formal parameter is
    constrained by these bounds (see 3.6.1)..."

RM 3.6.1(9):
   "For a formal parameter of a subprogram or entry, the bounds are
    obtained from the corresponding actual parameter. (The formal
    parameter is constrained with the corresponding values of the
    bounds)."

RM 6.2(9):
    "...the formal parameter is unconstrained if and only if the mode is IN OUT
     or OUT and the variable name given in the actual parameter denotes an
     unconstrained variable"

The above citations indicate that the formal parameter does have bounds
and that it is constrained, but doesn't say that the effect is a constrained
subtype.

So, what is the subtype of OBJECT?  Is it constrained or not?

-- Tim H.