Added new routine.

Compare two one dimensional cells of strings and count the number of common strings. The
optional second argument returns a formated list of common variables.

*Example*

If we have:

A = {'A1'; 'A2'; 'A3'; 'A4'; 'A5'; 'A6'};
B = {'B1'; 'A2'; 'B3'; 'A4'; 'A1'};

then

[n,message] = common_strings_in_cell_arrays(A,B);

returns n=3 and message='A2, A4 and A1'.

matlab/common_strings_in_cell_arrays.m

+function [n,message] = common_strings_in_cell_arrays(a,b)
+
+%@info:
+%! @deftypefn {Function File} {[@var{n}, @var{message} ] =} common_strings_in_cell_arrays (@var{a}, @var{b})
+%! @anchor{common_strings_in_cell_arrays}
+%! @sp 1
+%! Counts the number of common strings in two cell arrays of strings @var{a} and @var{b}. 
+%! @sp 2
+%! @strong{Inputs}
+%! @sp 1
+%! @table @ @var
+%! @item a
+%! One dimensional cell array of strings.
+%! @item b
+%! One dimensional cell array of strings.
+%! @end table
+%! @sp 2
+%! @strong{Outputs}
+%! @sp 1
+%! @table @ @var
+%! @item n
+%! Scalar integer, number of common strings.
+%! @item message
+%! String, formatted list of common strings. 
+%! @end table
+%! @end deftypefn
+%@eod:
+
+% Copyright (C) 2013 Dynare Team
+%
+% This file is part of Dynare.
+%
+% Dynare is free software: you can redistribute it and/or modify
+% it under the terms of the GNU General Public License as published by
+% the Free Software Foundation, either version 3 of the License, or
+% (at your option) any later version.
+%
+% Dynare is distributed in the hope that it will be useful,
+% but WITHOUT ANY WARRANTY; without even the implied warranty of
+% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+% GNU General Public License for more details.
+%
+% You should have received a copy of the GNU General Public License
+% along with Dynare.  If not, see <http://www.gnu.org/licenses/>.
+
+common_strings = intersect(a,b);
+n = numel(common_strings);
+
+if nargout>1
+    switch n
+      case 0
+        message = [];
+      case 1
+        message = common_strings{1};
+      case 2
+        message = [common_strings{1} ' and ' common_strings{2}];
+      otherwise
+        message = common_strings{1};
+        for i = 2:n-1
+            message = [message ', ' common_strings{i}];
+        end
+        message = [message ' and ' common_strings{n}];
+    end
+end
+
+%@test:1
+%$ % Define cell arrays of strings.
+%$ A = {'A1'; 'A2'; 'A3'; 'A4'};
+%$ B = {'B1'; 'B2'; 'B3'; 'B4'};
+%$
+%$ try
+%$    n = common_strings_in_cell_arrays(A,B);
+%$    [m,message] = common_strings_in_cell_arrays(A,B);
+%$    t(1) = 1;
+%$ catch
+%$    t = 0;
+%$ end
+%$
+%$ if length(t)>1
+%$    t(2) = dyn_assert(n,m);
+%$    t(3) = dyn_assert(n,0);
+%$    t(4) = dyn_assert(isempty(message),1);
+%$ end
+%$ T = all(t);
+%@eof:1
+
+%@test:2
+%$ % Define cell arrays of strings.
+%$ A = {'A1'; 'A2'; 'A3'; 'A4'};
+%$ B = {'B1'; 'A2'; 'B3'; 'A4'};
+%$
+%$ try
+%$    n = common_strings_in_cell_arrays(A,B);
+%$    [m,message] = common_strings_in_cell_arrays(A,B);
+%$    t(1) = 1;
+%$ catch
+%$    t = 0;
+%$ end
+%$
+%$ if length(t)>1
+%$    t(2) = dyn_assert(n,m);
+%$    t(3) = dyn_assert(n,2);
+%$    t(4) = dyn_assert(message,'A2 and A4');
+%$ end
+%$ T = all(t);
+%@eof:2
+
+%@test:2
+%$ % Define cell arrays of strings.
+%$ A = {'A1'; 'A2'; 'A3'; 'A4'; 'A5'; 'A6'};
+%$ B = {'B1'; 'A2'; 'B3'; 'A4'; 'A1'};
+%$
+%$ try
+%$    n = common_strings_in_cell_arrays(A,B);
+%$    [m,message] = common_strings_in_cell_arrays(A,B);
+%$    t(1) = 1;
+%$ catch
+%$    t = 0;
+%$ end
+%$
+%$ if length(t)>1
+%$    t(2) = dyn_assert(n,m);
+%$    t(3) = dyn_assert(n,3);
+%$    t(4) = dyn_assert(message,'A2, A4 and A1');
+%$ end
+%$ T = all(t);
+%@eof:3
+