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From: "G.B." <bauhaus@notmyhomepage.invalid>
Newsgroups: comp.lang.ada
Subject: Re: A function that cannot be called?
Date: Tue, 23 Oct 2018 13:45:25 +0200
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Xref: reader02.eternal-september.org comp.lang.ada:54695
Date: 2018-10-23T13:45:25+02:00
List-Id: <comp.lang.ada>

On 21.10.18 13:30, Egil H H wrote:

> package What is
>     pragma Assertion_Policy(Check);
> 
>     type Void is private with Type_Invariant => False;
>     
>     function Impossible return Void with Pre => False;
>     
> private
>     
>     type Void is null record;
>     
> end What;

This approach maybe illustrates a point best: in which way
does Ada's type system support detecting errors in a program
early? Or is is SPARK's type system? Compile time will be best.

It is tricky to explore empirically, though, since by experiments
I have got two different bug boxes so far. On this account, I'm
not sure if I can take 'Access of a function because seemingly
doing so triggers testing theprecondition...