function [wrap, unwrap] = arg_wrappers(varargin)
%ARG_WRAPPERS return functions to turn multiple arrays into a vector and back
%
% [wrap, unwrap] = arg_wrappers(varargin)
%
% Give this function an example list of arrays/matrices.
% It will return two functions:
% "wrap" will take a list of arrays/matrices with the same sizes and return them
% squished into a single column vector; "unwrap" will take the column vector and
% return a cell array of arrays with the same sizes as the example list.
%
% Example usage:
% >> [wrap, unwrap] = arg_wrappers(ones(2,3), ones(2,1));
% > X = wrap([1,4,5;2,7,8], [2;3])'
% X =
%      1     2     4     7     5     8     2     3
% >> [a, b] = celldeal(unwrap(X))
% a =
%      1     4     5
%      2     7     8
% b =
%      2
%      3
%
% Intended use: providing generic routines, such as optimizers, with column
% vectors, while making application-specific routines, such as cost functions,
% not have to worry about the packing and unpacking of multiple parameters with
% different sizes.

% Iain Murray, November 2007

% I always return the same function for wrap, but I think it's nice to always
% get the pair together, hence it being returned here rather than being a
% separate function:
wrap = @(varargin) cell2mat(cellmap(@(y) y(:)', varargin))';

% The unwrapping function depends on the sizes currently in use, so
% constructing this function is somewhat more complicated:
sizes = cellmap(@size, varargin);
volumes = cellfun(@prod, sizes);
ends = cumsum(volumes);
starts = cumsum([1, volumes(1:end-1)]);
ranges = num2cell([starts; ends], 1);

% Black magic, sorry!
%unwrap = @(x) celldeal(cellmap(@(z, n) reshape(z, sizes{n}), ...
%    cellmap(@(y) x(y(1):y(2)), ranges), num2cell(1:length(sizes))));
unwrap = @(x) cellmap(@(z, n) reshape(z, sizes{n}), ...
    cellmap(@(y) x(y(1):y(2)), ranges), num2cell(1:length(sizes)));