expression templates vs D arrays

[Walter Bright]

On 12/7/2011 11:11 PM, Robert Jacques wrote:
> On Wed, 07 Dec 2011 23:27:41 -0500, Jay Norwood <jayn at prismnet.com> wrote:
>
>> I've been reading about the use of expression templates in this blitz page,
>> which provides arrays implemented by c++ templates. They have some convenient
>> features, such as array initialization with auto-incrementing array index
>> values in the expressions and applying a cast operator to an entire array
>> within an expression. Do D built-in array operations and initialization
>> include these type of features, or would you need to create some similar D
>> template implementation to guarantee the efficient expression evaluation and
>> similar initialization features?
>>
>> http://www.oonumerics.org/blitz/docs/blitz_3.html#SEC80
>>
>
> Built-in? No, not everything. But std.range, std.array and std.algorithm have a
> lot of the convenience features you're looking for. Actual D array operations,
> i.e. x[] = y[] + z[] * b;, are more efficient than expression templates.
> Currently, what you can do in an array op is somewhat limited, but
> generalization, i.e. x[] = sin(iota(0,x.length)[]) + y[] is on Don's todo list.

I'll add that you can do expression templates in D, but there's no point to them.