----- Original Message ----- From: "Stewart, Robert" <Robert.Stewart@sig.com> To: <boost@lists.boost.org> Sent: Friday, May 15, 2009 6:16 PM Subject: Re: [boost] [array] assignement operator
vicente.botet wrote: On Friday, May 15, 2009 11:46 AM
Is the following more intuitive?
array<int,10> a; array<int, 5> b;
as_sub_array<0,4>(a) = b; // or b=as_sub_array<2,6>(a);
I like that idea, though I'd name it "subarray." I'd expect these to fail at compile time:
subarray<0,4>(a) = b; b = subarray<0,4>;
but not these:
subarray<0,5>(a) = b; b = subarray<0,5>(a);
Thus, I see subarray as having its size specified by the second template parameter and the offset into the array as the first template parameter.
This should also be possible:
subarray<6,3>(a) = subarray<1,3>(b);
Notice how the "3" matches in that statement, clearly showing that the two subarrays have the same length.
Yeah, this is clear. We can have a class 'subarray_view' and a factory function 'subarray'. subarray_view is a kind of static range.
The suggested idea may have its uses, but it has sufficiently odd behavior that it ought not to be a member function and certainly not the copy assignment operator. Perhaps a free function is in order.
Do you think that an specialization of a assign_to function would be intuitive
array<int, 5> a; array<int, 2> b; // ... assign_to(b,a); // or
assign_to(b,as_sub_array<0,1>a);
I don't like that. The argument order isn't intuitive and the odd behavior isn't made clear by the name. Besides, I think subarray handles every use case and makes the subset assignment behavior clear.
You are right, in order to have b = subarray<0,5>(a); efficient we need to overload the assignement operator on the array class. If no modification is made on the array class an 'assign' function can always be implemented efficiently. assign(b,subarray<0,5>(a)); Thanks, Vicente