On 4/18/18 3:15 AM, Simen Kjærås wrote:
On Wednesday, 18 April 2018 at 06:54:29 UTC, Chris Katko wrote:
I need to rotate an array by 90 degrees, or have writefln figure that
out.
I need, say:
0 4 5 6
0 0 0 0
0 0 0 0
0 0 0 0
But it's outputting:
0 0 0 0
4 0 0 0
5 0 0 0
6 0 0 0
int [4][4] data;
file.writeln(format("%(%-(%d %)\n%)", data));
Generally, the solution would be std.range.transposed. However, since
you're using a int[4][4], that's not a range-of-ranges, and transposed
don't work out of the box. This helper function should help:
T[][] ror(T, size_t N1, size_t N2)(ref T[N1][N2] arr)
{
T[][] result = new T[][N2];
foreach (i, e; arr) {
result[i] = e.dup;
}
return result;
}
unittest
{
import std.stdio;
import std.range;
int [4][4] data;
data[2][3] = 4;
writefln("%(%-(%d %)\n%)", data);
writefln("%(%-(%d %)\n%)", data.ror.transposed);
}
A version without allocating:
T[][N2] ror(T, size_t N1, size_t N2)(ref T[N1][N2] arr)
{
T[][N2] result;
foreach (i, ref e; arr) {
result[i] = e[];
}
return result;
}
...
writefln("%(%-(%d %)\n%)" data.ror[].transposed); // need the slice
operator here
Keep in mind, you can't simply assign a variable to data.ror[], as the
backing goes away immediately (OK to use as an rvalue though). And you
must keep data in scope as long as you are using the result of data.ror.
-Steve
