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Newsgroups: comp.lang.ada
Date: Fri, 29 Mar 2019 13:51:46 -0700 (PDT)
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Subject: Re: type definition for an integer with discrete range
From: mario.blunk.gplus@gmail.com
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Xref: reader01.eternal-september.org comp.lang.ada:56005
Date: 2019-03-29T13:51:46-07:00
List-Id: <comp.lang.ada>

On Friday, March 29, 2019 at 9:24:38 PM UTC+1, Simon Wright wrote:
> tra.....g@gmail.com writes:
> 
> > On Friday, March 29, 2019 at 11:10:42 PM UTC+7, mario.b...@gmail.com wrote:
> >> Hello,
> >> I'm looking for a way to define a type that runs from let say -100
> >> to +100 with gaps of 5 width. Important is to make sure that a value
> >> like 7 can not be assigned to the type.
> >>
> >> something like:
> >>
> >> type number is new integer range -100 .. 100;
> >> -- or
> >> subtype number is integer range -100 .. 100;
> >>
> >> -- with this special thing or something like that:
> >> for number'small use 5; -- can not applied here. works with fixed
> >> point types only
> >>
> >> Thanks !
> >
> > That's a fixed point type.
> 
> In Ada, that's an integer type. You can tell a real type because its
> literals *must* have a decimal point in them. Fixed- and floating-point
> types are both real types.
> 
> Mario's code might look like
> 
>   Number_Small : constant := 5.0;
>   type Number is delta Number_Small range -100.0 .. 100.0;
>   for Number'Small use Number_Small;

The problem is that you can assign a variable of type Number 101.0 without getting a compile error. I wrote a test program at
https://github.com/Blunk-electronic/ada_training/blob/master/src/type_angle/type_angle.adb
where the issue can be tested by yourself. Thanks !