Re: How to get a compilation error

["Jean-Pierre Rosen" <rosen@adalog.fr>]

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"Martin Dowie" <martin.dowie@nospam.baesystems.com> a �crit dans le message news: 3bf3d68c$1@pull.gecm.com...
> "Wilhelm Spickermann" <wilhelm.spickermann@t-online.de> wrote in message
> news:mailman.1005833842.603.comp.lang.ada@ada.eu.org...
> Hi,
>
> I would like to get a compilation *error*, if some compile time
> constant is not suitable for the algorithm in use. Example:
>
> Chunk_Bits : constant :=
>   Integer'Min (32, System.Max_Binary_Modulus / 2);
> type Check is (Checkitem1, Checkitem2);
> for Check'SIZE use 1 - Integer'MIN (96 mod Chunk_Bits, 1);
>
> The last two lines result in a compilation error, if and (I
> hope) only if 96 is not a multiple of Chunk_Bits. That�s what I
> want -- but it�s really ugly. Does anyone have something better?
>
>
> Could try:
>
>    type A_Valid_Range is range 0 .. 0;
>
>    My_Check : constant A_Valid_Range :=
>       A_Valid_Range (96 mod (Integer'Min (32, System.Max_Binary_Modulus /
> 2)));
>
> This will probably raise a warning rather than an error though.
> Some compilers will let you specify that warning are to be
> treated as errors.
To get an error, do the following:
subtype Assert is boolean range True..True;
Check : constant := Assert'Pos(96 rem Chunk_Bits = 0)

Since Check is a named number, an invalid value will result in a compile time error (new in 95).

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           J-P. Rosen (rosen@adalog.fr)
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