http://d.puremagic.com/issues/show_bug.cgi?id=10129

           Summary: problem with short numbers operator
           Product: D
           Version: D2
          Platform: x86_64
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: udefranettet@gmail.com


--- Comment #0 from cbr <udefranettet@gmail.com> 2013-05-21 12:11:12 PDT ---
Created an attachment (id=1215)
compile error for small number types

I would expect that it is allow to use the operator + and -.
on byte,ubyte,short and ushort numbers by dmd (and gdc) convert those to an
int.

The attach example gives the following complier error.
short_int_test.d(8): Error: cannot implicitly convert expression (cast(int)n +
cast(int)k) of type int to ubyte

When the Num alias is ubyte,byte,ushort and short.

So if we what to use those type we have to cast to an int isn't this a little overkill.

So instead of

 r=n+k;
We have to write.
 r=cast(Num)(n+k);
Where r,n,k is the to of Num.

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bearophile_hugs@eml.cc changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bearophile_hugs@eml.cc


--- Comment #1 from bearophile_hugs@eml.cc 2013-05-21 12:21:19 PDT ---
I am compiling this program, and I don't see errors or warnings:


void main() {
    alias Num = uint;
    Num n = 12;
    Num k = 11;
    Num r;
    r = n - k;
}

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Steven Schveighoffer <schveiguy@yahoo.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |schveiguy@yahoo.com
         Resolution|                            |INVALID


--- Comment #2 from Steven Schveighoffer <schveiguy@yahoo.com> 2013-05-21 12:42:53 PDT ---
The CPU does math at an integer level.  So what happens is, short, ushort, byte, and ubyte are integer promoted to int, then the operation is performed. After the operation, the number may or may not fit into the short, ushort, byte, or ubyte.  So the compiler requires a cast so you can verify "yes, I know I'm throwing away data."

This is working as expected.

(In reply to comment #1)
> I am compiling this program, and I don't see errors or warnings:

Right, the report states you have to change Num to byte, ubyte, short, or ushort.  Probably the attachment should be one of those.

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