Matlab: Variable-length input argument (varargin) list checking.

vararginChecking.m

%%  checking minimum arguments requried
minargs = 3;
maxargs = inf;
n_exargs = length(varargin);

try
    narginchk(minargs, maxargs);
catch err
    if strcmp(err.identifier,'MATLAB:narginchk:notEnoughInputs')
        error('batchconvert:notEnoughInputs',...
            'Not enough inputs, at least %d arguments are needed. Including indir, outdir and function handle.',minargs);
    else
        rethrow(err);
    end
end

%%  default parameters
opts = struct('samebasename', true, 'sameextension', true,...
              'inputextension', '', 'outputextension', '',...
              'startwith', '', 'endwith', '',...
              'verbose', false);
optnames = fieldnames(opts); %   case insensitive

%%  override default parameters
if rem(n_exargs,2)  % odd number of name/value
    error('batchconvert:notParameterValuePairs',...
          'Arguments after first %d should be parameter name/value pairs.',...
          minargs);
end
for pair = reshape(varargin,2,[])
    inoptname = lower(pair{1}); %   making it case insensitive
    if validatestring(inoptname, optnames)
        opts.(inoptname) = pair{2};
    else
        error('batchconvert:invalidparameter','%s is not a valid parameter.',...
              inoptname);
    end
end