On Saturday, July 28, 2012 09:58:32 Philip Daniels wrote:
> I have an array of objects that have a size() property. Code to
> sum them manually works fine, as expected:
>
> auto total = 0;
> foreach (wt; _word_tables)
> total += wt.size();
> return total;
>
>
> How can I do this with reduce? (BTW I second the old comments and
> bugs about not having sum() built into the library, it's
> annoying.)
>
> I tried
>
> auto total = reduce!(
> (int a, WordTable b) { return a + b.size(); })
> (0, _word_tables);
>
> but it seems that reduce expects a and b to be of type WordTable,
> so it won't instantiate the template. It's also as long as the
> manual version :-(
>
> I really want to do
>
> auto total = sum(a => a.size(), _word_tables)
>
> if that's possible.
How about
import std.algorithm;
import std.array;
import std.stdio;
void main()
{
auto stuff = ["hello world",
"Goodbye, Shirley",
"Babylon 5 rocks"];
auto result = reduce!"a + b.length"(0L, stuff);
assert(result == join(stuff).length);
}
The first parameter is the sum, and the second is the item. So, I expect that
auto total = reduce!((a, b) => a + b.size())(0, _word_tables);
would work for you.
- Jonathan M Davis
