checkstrs.m

A toolbox for the non-local means algorithm

function out = checkstrs(in, valid_strings, function_name, ...
                         variable_name, argument_position)
%CHECKSTRS Check validity of option string.
%   OUT = CHECKSTRS(IN,VALID_STRINGS,FUNCTION_NAME,VARIABLE_NAME, ...
%   ARGUMENT_POSITION) checks the validity of the option string IN.  It
%   returns the matching string in VALID_STRINGS in OUT.  CHECKSTRS looks
%   for a case-insensitive nonambiguous match between IN and the strings
%   in VALID_STRINGS.
%
%   VALID_STRINGS is a cell array containing strings.
%
%   FUNCTION_NAME is a string containing the function name to be used in the
%   formatted error message.
%
%   VARIABLE_NAME is a string containing the documented variable name to be
%   used in the formatted error message.
%
%   ARGUMENT_POSITION is a positive integer indicating which input argument
%   is being checked; it is also used in the formatted error message.

%   Copyright 1993-2003 The MathWorks, Inc.
%   $Revision: 1.3.4.4 $  $Date: 2003/05/03 17:51:45 $

% Except for IN, input arguments are not checked for validity.

% checkinput(in, 'char', 'row', function_name, variable_name, argument_position);

start = regexpi(valid_strings, ['^' in]);
if ~iscell(start)
    start = {start};
end
matches = ~cellfun('isempty',start);
idx = find(matches);

num_matches = length(idx);

if num_matches == 1
    out = valid_strings{idx};

else
    out = substringMatch(valid_strings(idx));
    
    if isempty(out)
        % Convert valid_strings to a single string containing a space-separated list
        % of valid strings.
        list = '';
        for k = 1:length(valid_strings)
            list = [list ', ' valid_strings{k}];
        end
        list(1:2) = [];
        
        msg1 = sprintf('Function %s expected its %s input argument, %s,', ...
                       upper(function_name), num2ordinal(argument_position), ...
                       variable_name);
        msg2 = 'to match one of these strings:';
        
        if num_matches == 0
            msg3 = sprintf('The input, ''%s'', did not match any of the valid strings.', in);
            id = sprintf('Images:%s:unrecognizedStringChoice', function_name);
            
        else
            msg3 = sprintf('The input, ''%s'', matched more than one valid string.', in);
            id = sprintf('Images:%s:ambiguousStringChoice', function_name);
        end
        
        error(id,'%s\n%s\n\n  %s\n\n%s', msg1, msg2, list, msg3);
    end
end

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
function str = substringMatch(strings)
%   STR = substringMatch(STRINGS) looks at STRINGS (a cell array of
%   strings) to see whether the shortest string is a proper substring of
%   all the other strings.  If it is, then substringMatch returns the
%   shortest string; otherwise, it returns the empty string.

if isempty(strings)
    str = '';
else
    len = cellfun('prodofsize',strings);
    [tmp,sortIdx] = sort(len);
    strings = strings(sortIdx);
    
    start = regexpi(strings(2:end), ['^' strings{1}]);
    if isempty(start) || (iscell(start) && any(cellfun('isempty',start)))
        str = '';
    else
        str = strings{1};
    end
end