Permutation with sets of elements

[cactuar]

I want to write a code to find the permutation of these sets:
A {A1, A2}
B {B1, B2}
C {C1, C2}

I want to keep the order of A, B, C, but want to get the permutation of the elements like:
A1, B1, C1
A1, B1, C2
A1, B2, C1
A1, B2, C2
A2, B1, C1
A2, B1, C2
A2, B2, C1
A2, B2, C2

I can't figure out the algorithm to do this! Please help!!

[EverBeginner]

High!

I would begin with this order :
A1, A2, B1, B2, C1, C2, ...
0 1 2 3 4 5, 6...
after that on comparing a range within an order went to an element of the order.
Also should have been aware of the limit that is actually as vast as unseen one.
And repeatedly.