Re: Learning Ada

[anon@anon.org (anon)]

Yes, I did redefine apart of Standard. Found this out back in the mid 1990 
while testing GNAT 3.0x for a number of projects. Its also, one way (not the 
best, but it is quick) of porting code from a 32-bit system down to a 16 or 
8 bit system. Like using Intel Core i7 system to write code for an Intel 
8086 system, which can use the same basic (non-protective mode) 
instruction set. 

Also, rewriting any Ada package is allowable within the scope of the RM 
(in some implementation it maybe required). And if I add a body for the 
Standard package and uncommented the an operators I could of made the 
operator do what I wanted it to do. Like having all Boolean operators 
return FALSE. 

This process does not hide the built-in Standard package, its still there for 
the system to handle the other types, such as the Character or 
Wide_Character set, which can be a headache to define.


In <ba7f8fc3-e386-49cc-a1fb-e53f7e1f04bf@d32g2000yqh.googlegroups.com>, AdaMagica <christoph.grein@eurocopter.com> writes:
>Oh my dear anon, you are so wrong again.
>
>> package STANDARD is
>>
>> =A0 -- The universal type universal_integer is predefined. =A0
>>
>> =A0 type INTEGER is range - 2 ** 63 .. ( 2 ** 63 ) - 1 ;
>>
>> end STANDARD;
>
>You do *not* redefine Standard with this declaration, you simply hide
>it.
>
>with Standard;
>
>procedure Temp is  -- Here you will get into troubled water.
>
>  X: Integer;  -- this is still the integer from the predefined
>package Standard
>  Y: STANDARD.Integer;  -- this is your INTEGER
>
>  use Standard;
>
>  Z: Integer :=3D 2;  -- oh lord, what's this now?
>
>  -- I'm not sure and I'm reluctant to do the RM exegesis to find out.
>I *guess* it's your INTEGER;
>
>  I: Integer :=3D Z**3;  -- subtype of 3 is still the Integer defined in
>                       -- the predefined Standard you've hidden
>  J: Integer :=3D Z**Z;  -- This should then be illegal because the
>subtype of the right operand of **
>                       -- must be the one from the hidden Standard.
>
>end Temp;
>
>Point is: You cannot redefine Standard! Full stop.
>
>I invite you to find the relevant paragraphs in the RM which state
>what will happen when you define a package named Standard.
>
>And please be careful to not mix up a subtype and the type of the
>subtype and the type of numeric literals. They are all different.