checkparams.m

approximate reinforcement learning

function s = checkparams(s, defaults, required)
%Verifies parameter structure and sets defaults for optional parameters
%  [S] = CHECKPARAMS(S, DEFAULTS, REQUIRED)
%  Verifies a parameter structure for required fields and sets defaults for
%  optional fields. Emits an error if any required field is missing.
%  
%  Parameters:
%   S           - the parameters structure to check
%   DEFAULTS    - the default values for optional parameters, a structure
%               with the same field names for parameters as those expected
%               in S. Can contain nested structures. Can be an empty matrix,
%               in which case no defaults are installed but the required fields
%               are verified.
%   REQUIRED    - the names of the required parameters, cell array of
%               strings
%
%  Note that type verifications are not performed; e.g. if a numeric is in
%  place of a structure, it will be handled as a structure and as a result
%  an (unaddressed) error will occur.
%
%  Returns:
%   S           - the parameters structure with the missing values replaced
%               by defaults
%
%  Author:      Lucian Busoniu
%  Version:     1.0
%  History:

REQARGIN = 2;
if nargin < REQARGIN + 1,
    required = {};
end;

for i = 1 : length(required)
    if ~isfield(s, required{i})
        error(['Field ' required{i} ' is required']);
    end;
end;

if isempty(defaults), return; end;

fld = fieldnames(defaults);
for i = 1 : length(fld)
    if ~isfield(s, fld{i})            % assign defaults
        s.(fld{i}) = defaults.(fld{i});
    elseif isstruct(s.(fld{i})),      % process recursively for defaults
        s.(fld{i}) = checkparams(s.(fld{i}), defaults.(fld{i}));
    end;
end;