Re: unsigned type

[anon@anon.org (anon)]

"Natural" "Positive" definition: come from Mathematics and for Ada the Ada 
Language reference Manual ( Ada RM ) define in the Standard package.
 
And all packages are defines as a child of the Standard package. Now for the 
Integer, Natural and Positive data types the value for a 32-bit system follows
And in a 64 bit system the types would be based on "2 ** 64" instead of
"2 ** 32". 

package Standard is

   type Integer is range -(2 ** 31) .. +(2 ** 31 - 1);

   subtype Natural  is Integer range 0 .. +(2 ** 31 - 1);
   subtype Positive is Integer range 1 .. +(2 ** 31 - 1);
 ...
end Standard ;


In <1eS1m.2153$j84.1865@nlpi061.nbdc.sbc.com>, Gary Scott <garylscott@sbcglobal.net> writes:
>tmoran@acm.org wrote:
>
>>>I am trying to declare a type as unsigned using Ubuntu 9.04 GNAT
>>>compiler.  I know Ada does not have a type CARDINAL, but I thought it
>>>had a type Unsigned.
>> 
>> 
>> Ada's equivalent is Natural.  If
>
>Sorry for the naive question.  I'm curious as to the reason for the term 
>"natural".  "Unnatural" would seem more descriptive :)
>
>
>>   Lowest : Natural := 0;
>>   Highest : Natural := Natural'last;
>> then
>>   Lowest  := Lowest-1;  -- will raise an exception
>>   Highest := Highest+1; -- ditto
>> 
>> (Note that Gnat by default is not a legal Ada compiler because it doesn't
>> check for and raise the exception.  You need a command line parameter
>> -gnato to make it act like Ada.)
>> 
>> The standard Ada package Interfaces has hardware-oriented types
>> Unsigned_8, Unsigned_16, etc but those are modular types so if
>>   Empty_Word : Interfaces.Unsigned_16 := 0;
>>   Full_Byte  : Interfaces.Unsigned_8 := 255;
>> then
>>   Empty_Word-1 will be 65535.
>>   Full_Byte+1 will be 0.
>> with no exceptions raised.
>> 
>> You can also declare your own application oriented non-negative types
>>   type Ratings is range 1 .. 10;
>> or modular types
>>   type Degrees is mod 360;  -- 0 .. 359 wrapping around
>
>
>-- 
>
>Gary Scott
>mailto:garylscott@sbcglobal dot net
>
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>
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>
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