On Tuesday, 11 December 2012 at 16:09:14 UTC, Andrei Alexandrescu
wrote:
On 12/11/12 8:24 AM, d coder wrote:
No, it's a fix of a gotcha from C. The C code would just
allow the
assignment.
Yes Andrei.
But it does not look clean if you have to write:
byte a, b, c;
a = cast(byte) (b + c);
Well I know the advantages (safety). But imagine having to
write all
that when working with bytes and shorts. Makes it really
difficult to
work with shorts and bytes in D.
Value range propagation automatically avoids the need for a lot
of those casts.
http://www.drdobbs.com/tools/value-range-propagation/229300211
Would I be asking for too much if I ask
DMD to provide a compiler flag that makes it return bytes and
shorts for
operations on them?
That won't happen.
Andrei
But than we have a bug in the value range propagation algorithm.
E.g in the original program:
void main()
{
import std.stdio;
ushort a = 0x55AA;
ushort b = 0xAA55;
writefln("%X", ~(a | b));
}
(a | b) will be in the range of ushort values and ~ of that also
remains in the same value range. In other words, it makes no
sense that boolean ops (and, or, xor, 1's compliment, 2's
compliment) will require type promotion as they cannot exceed the
original width of the values. This is unlike arithmetic which can
require promotion.
