On Saturday, 3 August 2013 at 13:46:38 UTC, David Nadlinger wrote:
On Saturday, 3 August 2013 at 13:35:56 UTC, Andre Artus wrote:
import std.stdio;
import std.algorithm;
void main()
{
auto values = [ 1, 2, 3, 4, 5 ];
writeln(values
.map!(a => a * 10)
.map!(a => a / 3)
.filter!(a => !(a % 2)));
}
As stated this implies 3 separate traversals of the list (or
array to be specific) which is what a naïve implementation
would do.
In this example, no, as all involved ranges are evaluated
lazily. (I see your general point, though.)
David
I probably could have worded it better: I did not intend to imply
that D follows the naïve implementation suggested. What I meant
is that, on the face of it, given typical textbook
implementations of map and filter you would be iterating 3
separate times. To be clear I don't know of any serious
implementations of these algorithms that do not address this in
some way.
