function [params, netconfig] = stack2params(stack)

% Converts a "stack" structure into a flattened parameter vector and also

% stores the network configuration. This is useful when working with

% optimization toolboxes such as minFunc.

%

% [params, netconfig] = stack2params(stack)

%

% stack - the stack structure, where stack{1}.w = weights of first layer

%                                    stack{1}.b = weights of first layer

%                                    stack{2}.w = weights of second layer

%                                    stack{2}.b = weights of second layer

%                                    ... etc.

% Setup the compressed param vector

params = [];

for d = 1:numel(stack)

    % This can be optimized. But since our stacks are relatively short, it

    % is okay

    params = [params ; stack{d}.w(:) ; stack{d}.b(:) ];

    % Check that stack is of the correct form

    assert(size(stack{d}.w, 1) == size(stack{d}.b, 1), ...

        ['The bias should be a *column* vector of ' ...

         int2str(size(stack{d}.w, 1)) 'x1']);

    if d < numel(stack)

        assert(size(stack{d}.w, 1) == size(stack{d+1}.w, 2), ...

            ['The adjacent layers L' int2str(d) ' and L' int2str(d+1) ...

             ' should have matching sizes.']);

    end

end

if nargout > 1

    % Setup netconfig

    if numel(stack) == 0

        netconfig.inputsize = 0;

        netconfig.layersizes = {};

    else

        netconfig.inputsize = size(stack{1}.w, 2);

        netconfig.layersizes = {};

        for d = 1:numel(stack)

            netconfig.layersizes = [netconfig.layersizes ; size(stack{d}.w,1)];

        end

    end

end

end