Re: Which compiler is right ?

[stt@houdini.camb.inmet.com (Tucker Taft)]

Strategies (strategies@magic.fr) wrote:

: Hello
: Is the following code legal ?

No.

: I have two compilers with two different answers

The one that rejects the program is correct.

: generic
:    type Element_Type is limited private;
:    type Index_Type is (<>);
:    type Element_Array is array (Index_Type range <>) of Element_Type;
:    with function Equal (Left, Right : Element_Type) 
: 	return Boolean is "=";   

When you give a default for a function like this (is "="), it is looked
up when the generic is compiled, as opposed to when it is instantiated.
And there is no "=" visible that matches the given parameter profile.

The only way to specify a default that is looked up when a generic
is instantiated is to use "is <>", and then the name of the formal
subprogram must match the name that you want looked up at the point
of instantiation.  Hence, you could do the following:

    with function "="(Left, Right : Element_Type) return Boolean is <>;

Now when you instantiate this generic, if the actual parameter is omitted
for this formal parameter, then the compiler will look for a directly
visible "=" that matches the given profile.

If you prefer to use the name "Equal" inside the generic, 
you could add a remame inside the generic body, such as:

    function Equal(Left, Right : Element_Type) return Boolean renames "=";

By the way, I agree with the other responder that when you have
a question like this, it sure makes it easier to help if you include
the error messages produced by the compiler(s) with your question.

: function Generic_Indice (Left  :
: Element_Type;                          			 Right : Element_Array) return
: Index_Type;
: -- 
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: -- Jerome HAGUET, Strategies, Rungis, France 			      --
: -- Tel : (33 1 | 01) 41 73 04 80  ;   Fax : (33 1 | 01) 41 73 04 99   --
: -- Internet : strategies@magic.fr ;   Compuserve : 100747,2001        --
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-Tucker Taft   stt@inmet.com   http://www.inmet.com/~stt/
Intermetrics, Inc.  Burlington, MA  USA