[M3devel] floating point : problem with Extended.m3
Mika Nystrom
mika at async.caltech.edu
Sun Apr 3 03:28:18 CEST 2011
Hello m3devel (mainly Tony),
I believe I've found a problem with float/Common/Extended.m3.
Doesn't the code assume that EXTENDED is a multiple of 32 bits wide?
That does not seem to me to be a safe assumption... in fact I don't
think it's even safe to round up. EXTENDED could (and should) be
10 bytes wide on most machines. (I am aware that it is currently
the same as LONGREAL, but...)
Mika
> UNSAFE MODULE Extended;
>
> IMPORT Word, Int32;
>
> PROCEDURE Equal(a, b: T): BOOLEAN =
> BEGIN RETURN a = b END Equal;
>
>
> CONST Int32Sz = BYTESIZE(T) DIV BYTESIZE(Int32.T);
>
> TYPE Int32Arr = ARRAY [0..Int32Sz-1] OF Int32.T;
>
> PROCEDURE Hash(a: T): Word.T =
> VAR arr := LOOPHOLE(a, Int32Arr); res := 0; BEGIN
> FOR i := 0 TO LAST(arr) DO
> res := Word.Xor(res, Int32.Hash(arr[i]))
> END (* FOR *);
> RETURN res
> END Hash;
>
> PROCEDURE Compare(a, b: T): [-1..1] =
> BEGIN
> IF a < b THEN RETURN -1
> ELSIF a > b THEN RETURN 1
> ELSE RETURN 0
> END (* IF *)
> END Compare;
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