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)

%!test
%! % Work around MATLAB bug where f(x)(y) is invalid syntax
%! % (This bug does not apply to Octave)
%!
%! C = @(fcn,x) fcn(x);
%! C2 = @(fcn,x,y) fcn(x,y);
%!
%! % Church Booleans
%! T = @(t,f) t;
%! F = @(t,f) f;
%!
%! % Church Numerals
%! Zero  = @(fcn,x) x;
%! One   = @(fcn,x) fcn(x);
%! Two   = @(fcn,x) fcn(fcn(x));
%! Three = @(fcn,x) fcn(fcn(fcn(x)));
%! Four  = @(fcn,x) fcn(fcn(fcn(fcn(x))));
%!
%! % Arithmetic Operations
%! Inc = @(a) @(f,x) f(a(f,x)); % Increment
%! Add = @(a,b) @(f,x) a(f,b(f,x));
%! Mult = @(a,b) @(f,x) a(@(x) b(f,x),x);
%! Dec = @(a) @(f,x) C(a(@(g) @(h) h(g(f)), @(u) x), @(u) u); % Decrement
%! Sub = @(a,b) b(Dec, a);
%!
%! % Renderer - Convert church numeral to "real" number
%! Render = @(n) n(@(n) n+1,0);
%!
%! % Predicates
%! Iszero = @(n) n(@(x) F, T);
%!
%! % Y combinator implements recursion
%! Ycomb = @(f) C(@(g) f(@(x) C(g(g), x)), ...
%!                @(g) f(@(x) C(g(g), x)));
%!
%! Factorial = Ycomb(@(f) @(n) C(C2(Iszero(n), ...
%!                   @(d) One, @(d) Mult(n, f(Dec(n)))),0));
%!
%! assert (Render (Factorial (Two)), 2)
%! assert (Render (Factorial (Three)), 6)
%! assert (Render (Factorial (Four)), 24)