[M3devel] TInt/TWord/m3back

[Tony Hosking]

This all speaks to your trying to use TInt for purposes it was never intended.  It is there in support of the compiler front-end not compiler back-ends.

On 25 Feb 2010, at 08:24, Jay K wrote:

> Tony, it should now be much closer to your intent.
>  I grant maybe the constants are misplaced, and I should try again to use ToBytes.
>  
>  
> I'm worried though.
> It used to be I could do:
>  
>  
> TInt.Add(Int{4,FF,FF,FF,7}, One)
> and be told it overflowed, in 4 bytes of precision.

You must check explicitly that there is no overflow.  This is easy enough.

TInt.LT(result, Target.Int32.min) OR TInt.LT(Target.Int32.max, result)

>  Now it'll just do it in 8 and no overflow.
>  
>  
> And chop always succeeds.
>  
> Maybe:
>  
>  
> PROCEDURE CheckChop (VAR r: Int;  n: CARDINAL) =
>   BEGIN
>     IF And (r [n-1], SignMask) = 0
>       THEN FOR i := n TO LAST(Int) DO IF r [i] # 0  THEN RETURN FALSE END; END;
>       ELSE FOR i := n TO LAST(Int) DO IF r [i] # Mask THEN RETURN FALSE END; END;
>     END;
>    RETURN TRUE;
>   END CheckChop;
> 
> ?
> 
>  - Jay

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