ASA172 is a FORTRAN90 library which generates all multidimensional indices in a given range. simulating the behavior of an arbitrary number of nested loops, by OFlaherty and MacKenzie.
If the number of dimensions was known in advance, such an operation could be carried out by the corresponding set of nested loops. For example, in 3D:
do i = i1, i2 do j = j1, j2 do k = k1, k2 (I,J,K) is an index in the range. end do end do end doOne feature of this library, though, is that it can generate all such indexes for an arbitrary number of dimensions.
ASA172 is Applied Statistics Algorithm 172.
ASA172 is available in a C version and a C++ version and a FORTRAN77 version and a FORTRAN90 version and a MATLAB version.
SUBSET, a FORTRAN90 library which enumerates combinations, partitions, subsets, index sets, trees, and other combinatorial objects.
Original FORTRAN77 version by M OFlaherty, G MacKenzie; FORTRAN90 version by John Burkardt.
You can go up one level to the FORTRAN90 source codes.