On Friday, 9 May 2014 at 15:52:51 UTC, John Colvin wrote:
On Friday, 9 May 2014 at 14:23:41 UTC, Luís Marques wrote:
If you have an array of structs, such as...
struct Foo
{
int x;
int y;
}
Foo[] foos;
...and you wanted to sort the foos then you'd do something
like...
foos.sort!(a.x < b.x),
..and, of course, both of the fields x and y get sorted
together.
If you have a so-called struct of arrays, or an equivalent
situation, such as...
int[] fooX;
int[] fooY;
...is there a simple way to sort fooX and fooY
"together"/coherently (keyed on, say, fooX), using the standard
lib?
For some situations (expensive/impossible to move/copy elements
of fooY), you would be best with this:
auto indices = zip(iota(fooX.length).array, fooX).sort!"a[1] <
b[1]".map!"a[0]";
auto sortedFooY = fooY.indexed(indices);
bearing in mind that this causes an allocation for the index,
but if you really can't move the elements of fooY (and fooX
isn't already indices of fooY) then you don't have much of a
choice.
It's probably better to use makeIndex:
http://dlang.org/phobos/std_algorithm.html#makeIndex
