Re: Ada Basics

[Jerry Petrey <"jdpetrey<NOSPAM>"@raytheon.com>]

prashna wrote:

> Hi all,
> What is the difference between declaring a type by using new (ex type
> one_to_hundred is new Integer range 1..100) and declaring a type
> without using new (type one_to_hundred is range 1..100)?
>
> Thanks in advance

The 'new' creates an explicit derived type which is a copy of the parent type
and inherits the primitive operations of the parent and any user defined
operations
of the parent before the derived type is defined.  It is a distinct type and
would
require a type conversion to be mixed with objects of the parent type, for
example.

In the example you cited, there would be little difference since all integer
types
are derived types - type one_to_hundred is range 1..100 creates a derived
type but the compiler chooses which predefined integer type to derive from (it
might for
example, choose short_integer).
With  one_to_hundred is new Integer range 1..100 , you are explicitly choosing

the parent type to be the predefined type Integer.

In Ada 95, derived types form the foundation of the polymorphic type
mechanism.
I would suggest you look at one of the good tutorials for more details on this

subject.  Look at http://www.adapower.org/ at the tutorials section.

Jerry
--
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-- Jerry Petrey
-- Senior Principal Systems Engineer - Navigation (GPS/INS), Guidance, &
Control
-- Raytheon Missile Systems          - Member Team Ada & Team Forth
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