Consider the generator of the selections:
for (i1 = 0; i1 < 10; i1++)
for (i2 = i1; i2 < 10; i2++)
for (i3 = i2; i3 < 10; i3++)
for (i4 = i3; i4 < 10; i4++)
printf("%d%d%d%d", i1, i2, i3, i4);
Result:
0000
0001
0002
...
0009
0011 <-- 0010 is skipped
0012
...
0019
0022 <-- 0020 and 0021 are skipped
0023
...
8999
9999
Generated selections have the following property: the order in the selection does not mater, i.e. 0011 0101 1001 1010 1100 are the same.
Basically it is 4-combination of the set { 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2, ..., 9, 9, 9, 9}
What do you say to name this type of the selection?
I always get stuck when I say:
4-xxxxxxxx of the set {0, 1, 2, ..., 9}
where xxxxxxxx is the name of this selection.