On Mon, 01 Nov 2010 03:50:12 -0400, Andreas Kaempf <andreas.kae...@web.de>
wrote:
Hey folks!
Please enlight me with that prefix notation of 2-dimensional arrays! I
prepared a snippet giving me headaches:
auto int[2][3] test = [[11,12],[21,22],[31,32]];
foreach (x, row; test)
{
Stdout.format("x={}: ", x+1);
foreach (y, cell; row)
{
Stdout.format("{}:({}) ", y+1, test[x][y]);
// Stdout.format("{}:({}) ", y+1, test[y][x]); // I expected this
here
according the declariation!
}
Stdout.newline;
}
According to the documentation, the declaration of test should declare 3
arrays of two ints. The initialization works fine so that's ok for me.
But why do I have to access it with test[x][y] to produce this result?
x=1: y=1:(11) y=2:(12)
x=2: y=1:(21) y=2:(22)
x=3: y=1:(31) y=2:(32)
This literally drives me crazy! I really want to understand that!
test is a 3-element array of 2-element arrays. When you index test, you
get a 2-element array as its element. When you index that, you get the
individual ints.
Think about it in terms of a single array. If you have an array of type
T[3], it's element type is T. So if T is int[2], then it appears
perfectly consistent:
int[2][3] t; // T is int[2]
auto x = t[0]; // T x is of type int[2]
As an aside, your foreach code is mighty inefficient. Each time through
the array, row is a copy of the original element, which means you are
moving a lot of data without ever using it.
I'd recommend using ref, like this:
foreach(x, ref row; test)
Unfortunately, you can't use the 0..test.length syntax since you are using
D1. You could use a straight for-loop.
-Steve
