function stack = params2stack(params, netconfig)

% Converts a flattened parameter vector into a nice "stack" structure 

% for us to work with. This is useful when you're building multilayer

% networks.

%

% stack = params2stack(params, netconfig)

%

% params - flattened parameter vector

% netconfig - auxiliary variable containing 

%             the configuration of the network

%

% Map the params (a vector into a stack of weights)

depth = numel(netconfig.layersizes);

stack = cell(depth,1);

prevLayerSize = netconfig.inputsize; % the size of the previous layer

curPos = double(1);                  % mark current position in parameter vector

for d = 1:depth

    % Create layer d

    stack{d} = struct;

    % Extract weights

    wlen = double(netconfig.layersizes{d} * prevLayerSize);

    stack{d}.w = reshape(params(curPos:curPos+wlen-1), netconfig.layersizes{d}, prevLayerSize);

    curPos = curPos+wlen;

    % Extract bias

    blen = double(netconfig.layersizes{d});

    stack{d}.b = reshape(params(curPos:curPos+blen-1), netconfig.layersizes{d}, 1);

    curPos = curPos+blen;

    % Set previous layer size

    prevLayerSize = netconfig.layersizes{d};

end

end