Re: [boost] [util] Any interest in address_of_first_nonarray_elem ?

On Sun, 01 Dec 2013 23:56:41 -0800, Joaquin M Lopez Munoz wrote:

Mostafa writes:

...

Working with built-in array objects I find myself repeatedly needing to get the address of the first non-array element. This is so I can do generic array comparisons and copies without resorting to multiple loops. For example:

template bool generic_array_equal(T (&lhs)[N], T const (&rhs)[N]) { return std::equal( address_of_first_nonarray_elem(lhs), address_of_first_nonarray_elem(lhs) + total_extent::size, address_of_first_nonarray_elem(rhs)); }

Any interest in adding such a function to the util library?

Why the "non"? Shouldn't the name be "address_of_first_array_elem"? How is this different from std::begin(lhs)?

No. The motivating use case for this were built-in multidimensional arrays. I wanted a generic way to compare and copy them without resorting to nested loops. For example: typedef int ArrType[2][3]; ArrType a1 = { {0, 1, 2}, {3, 4, 5} }; ArrType a2 = { {0, 1, 2}, {3, 4, 5} }; // Prints 0. std::cout << "Std Equal: " << std::equal(a1, a1 + 2, a2) << "\n"; // Prints 1. Obviously address_of_first_nonarray_elem would be used instead of subscripting. std::cout << "Flattened Std Equal: " << std::equal(a1[0], a1[0] + 6, a2[0]) << "\n"; In the above example the address of the first array element won't do, since that itself is an array. In general what is needed is the address of the first non-array element, and in the above case that would be &a1[0][0] or a1[0].