Mercurial > octave-nkf
view scripts/general/nthargout.m @ 20607:db3286201347 stable
doc: Add explanation of ':' optional input to numel().
* data.cc (Fnumel): Add explanation of ':' optional input.
author | Rik <rik@octave.org> |
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date | Wed, 07 Oct 2015 14:52:01 -0700 |
parents | 7503499a252b |
children |
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## Copyright (C) 2012-2015 Jordi GutiƩrrez Hermoso ## ## This file is part of Octave. ## ## Octave is free software; you can redistribute it and/or modify it ## under the terms of the GNU General Public License as published by ## the Free Software Foundation; either version 3 of the License, or (at ## your option) any later version. ## ## Octave is distributed in the hope that it will be useful, but ## WITHOUT ANY WARRANTY; without even the implied warranty of ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU ## General Public License for more details. ## ## You should have received a copy of the GNU General Public License ## along with Octave; see the file COPYING. If not, see ## <http://www.gnu.org/licenses/>. ## -*- texinfo -*- ## @deftypefn {Function File} {} nthargout (@var{n}, @var{func}, @dots{}) ## @deftypefnx {Function File} {} nthargout (@var{n}, @var{ntot}, @var{func}, @dots{}) ## Return the @var{n}th output argument of the function specified by the ## function handle or string @var{func}. ## ## Any additional arguments are passed directly to @var{func}. The total ## number of arguments to call @var{func} with can be passed in @var{ntot}; by ## default @var{ntot} is @var{n}. The input @var{n} can also be a vector of ## indices of the output, in which case the output will be a cell array of the ## requested output arguments. ## ## The intended use @code{nthargout} is to avoid intermediate variables. For ## example, when finding the indices of the maximum entry of a matrix, the ## following two compositions of nthargout ## ## @example ## @group ## @var{m} = magic (5); ## cell2mat (nthargout ([1, 2], @@ind2sub, size (@var{m}), ## nthargout (2, @@max, @var{m}(:)))) ## @result{} 5 3 ## @end group ## @end example ## ## @noindent ## are completely equivalent to the following lines: ## ## @example ## @group ## @var{m} = magic (5); ## [~, idx] = max (@var{M}(:)); ## [i, j] = ind2sub (size (@var{m}), idx); ## [i, j] ## @result{} 5 3 ## @end group ## @end example ## ## It can also be helpful to have all output arguments in a single cell in the ## following manner: ## ## @example ## @var{USV} = nthargout ([1:3], @@svd, hilb (5)); ## @end example ## ## @seealso{nargin, nargout, varargin, varargout, isargout} ## @end deftypefn ## Author: Jordi GutiƩrrez Hermoso function out = nthargout (n, varargin) if (nargin < 2) print_usage (); endif if (isa (varargin{1}, "function_handle") || ischar (varargin{1})) ntot = max (n(:)); func = varargin{1}; args = varargin(2:end); elseif (isnumeric (varargin{1}) && (isa (varargin{2}, "function_handle") || ischar (varargin{2}))) ntot = varargin{1}; func = varargin{2}; args = varargin(3:end); else print_usage (); endif if (any (n != fix (n)) || ntot != fix (ntot) || any (n <= 0) || ntot <= 0) error ("nthargout: N and NTOT must consist of positive integers"); endif outargs = cell (1, ntot); try [outargs{:}] = feval (func, args{:}); if (numel (n) > 1) out = outargs(n); else out = outargs{n}; endif catch err = lasterr (); if (strfind ("some elements undefined in return list", err)) error ("nthargout: Too many output arguments: %d", ntot); else error (err); endif end_try_catch endfunction %!shared m %! m = magic (5); %!assert (nthargout ([1,2], @ind2sub, size (m), nthargout (2, @max, m(:))), {5,3}) %!assert (nthargout (3, @find, m(m>20)), [23, 24, 25, 21, 22]')