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From: ucaa2385@iris3.csv.ica.uni-stuttgart.de (Peter Hermann)
Newsgroups: comp.lang.ada
Subject: Re: Q: common types?!
Date: 29 Sep 1994 11:37:11 GMT
Organization: Comp.Center (RUS), U of Stuttgart, FRG
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Date: 1994-09-29T11:37:11+00:00
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Tony Leavitt (tony@deepthought.Sgi.COM) wrote:
: This package would define all kinds of types for feet, nautical
: miles, degrees, radians, etc, ad nuasium, for all different kinds and sizes
: of float and integers.  Am I about to go insane by trying this?  Or, does

yes

:    type float64 is new float ;
:    for  float64'SIZE use 64 ;

The type float has been introduced as a predefined type which is 
different for each compiler/hardware and cannot be used
for portable programs. Coming from other languages without typing
system, the type float is offered in Ada for a first, unclean
solution which will be abandoned once the typing system 
is understood.
The above "rape" cannot work because the size of the root type
is fixed and cannot be changed for a subtype,
neither enlarged nor reduced.

You are "deriving" in any way from another type.
That means that you create a different type being incompatible
the the original type.

Therefore, for the same purpose, you easily write

    type my_float_type is digits 14 ; 
    or
    type my_float_type is digits 14 range 0.0 .. 1.234e7 ; 

for example.

--
Peter Hermann  Tel:+49-711-685-3611 Fax:3758 ph@csv.ica.uni-stuttgart.de
Pfaffenwaldring 27, 70569 Stuttgart Uni Computeranwendungen
Team Ada: "C'mon people let the world begin" (Paul McCartney)