All calls to "find" use the same generic implementation (bug #42408, 42421) * find.cc: Rewrite. Move generic "find" logic to find.h (Ffind) : Changed calls to find_nonzero_elem_idx to find_templated Added unit test for bug #42421 * Array.cc (and .h) (Array::find): Deleted function. Replaced with find::find(Array) from find.h * Array.h: Added typedef for array_iterator (in nz-iterators.h) as Array::iter_type * DiagArray2.h: Added typedef for diag_iterator (in nz-iterators.h) as DiagArray2::iter_type * PermMatrix.h: Added typedef for perm_iterator (in nz-iterators.h) as PermMatrix::iter_type Also added typedef for bool as PermMatrix::element_type (not octave_idx_type) Added an nnz() function (which is an alias for perm_length) and a perm_elem(i) function for retrieving the ith element of the permutation * Sparse.h: Added typedef for sparse_iterator (in nz-iterators.h) as Sparse::iter_type Added a short comment documenting the the argument to the numel function * idx-vector.cc (idx_vector::idx_mask_rep::as_array): Changed Array.find to find::find(Array) (in find.h) * (new file) find.h * (new file) interp-idx.h: Simple methods for converting between interpreter index type and internal octave_idx_type/row-col pair * (new file) min-with-nnz.h: Fast methods for taking an arbitrary matrix M and an octave_idx_type n and finding min(M.nnz(), n) * (new file) nz-iterators.h: Iterators for traversing (in column-major order) the nonzero elements of any array or matrix backwards or forwards * (new file) direction.h: Generic methods for simplifying code has to deal with a "backwards or forwards" template argument * build-sparse-tests.sh: Removed 5-return-value calls to "find" in unit-tests; Admittedly this commit breaks this "feature" which was undocumented and only partially supported to begin with (ie never worked for full matrices, permutation matrices, or diagonal matrices)