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From: =?ISO-8859-1?Q?Hibou57_=28Yannick_Duch=EAne=29?=
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Newsgroups: comp.lang.eiffel,comp.lang.ada
Subject: Re: Alternatives to C: ObjectPascal, Eiffel, Ada or Modula-3?
Date: Mon, 20 Jul 2009 11:49:16 -0700 (PDT)
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Date: 2009-07-20T11:49:16-07:00
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On 20 juil, 20:33, Cesar Rabak <csra...@yahoo.com.br> wrote:
> Here you create two "subtypes" which are only nicknames for Float in
> order to help the Ada compiler to discriminate the signature. BTW, why
> the need of two subtypes for coordinates?
Not =93 subtype =94 but =93 type =94, which is not the same. Ada has both, =
and
both are differents.

A type does not only designate a range of allowed values, it also
designate a source, which in turn, associate design property to it
(this can be asserted relying on type matching rules).

If you want to be sure what a function recieve only come from a
defined set of functions, then you define a type, some functions
returning value of this types, or procedure modifying this type. Two
types may seem similar at a quick sight, but types are not only used
to define ranges.

Types allow to define the valid flow of some objects or values, it
allows to make assertions about where it come from and where it can go
(thus, what was done with on/with it). This as to deal with the
overall design, the whole usage of a library, and not only with the
set of value allowed for a given type.

This is not a kind of nickname, this is a difference written in the
stone