std.bitmanip - bitshift?

[Steven Schveighoffer via Digitalmars-d-learn]

On 12/13/14 5:47 AM, "Marc =?UTF-8?B?U2Now7x0eiI=?= <schuetzm at gmx.net>" 
wrote:
> On Friday, 12 December 2014 at 19:35:26 UTC, Steven Schveighoffer wrote:
>> On 12/12/14 2:17 PM, H. S. Teoh via Digitalmars-d-learn wrote:
>>> I've started working on an implementation of this... but it's not very
>>> clear what the correct semantics should be. For example, if my starting
>>> BitArray b is 1101, say, what should be the result after b>>=1? Should
>>> it be 0110, 110, or 01101?
>>
>> 0110
>>
>> In other words, I would assume the same semantics as an unsigned int.
>>
>> In other other words, it's like each bit moves one to the right, and
>> the bit that has no source gets a 0.
>
> There's a dedicated >>> operator for unsigned right shift, the normal >>
> operator does a signed right shift, i.e. it copies the left-most bit:
> http://dlang.org/expression#ShiftExpression
>
> IMO, for consistency, bitarray should behave the same.

But BitArray is not signed, it's an array of bits, none of which are 
signed or designated as the sign bit. The unsigned shift operator is 
only for signed integral types, for unsigned values >> is simply a shift 
of bits. Note that your assertion that >> "copies the left-most bit" is 
not in the text, and is incorrect. It copies the sign bit, which doesn't 
exist in an unsigned type.

I think >> and >>> should do the same thing, and be unsigned shifts on 
BitArray.

-Steve