collapse(c)

function c = collapse(c)
%c = collapse(c)
%   Takes a recursive cell array as a tree and collapses any branches
%   having a fanout of 1.  Any elements with fanout of 0 are removed.
%
%Examples:
%   collapse({1 2 3})           --> {1 2 3}
%   collapse({{1} {2} {{3}}})   --> {1 2 3}
%   collapse({1 {2 3}})         --> {1 {2 3}}
%   collapse({1 {{} 2 {{}} 3}}) --> {1 {2 3}}
%   collapse({{{}}})            --> {}
%
%   [matches] = regexp({'abc', 'def', 'fghi'}, '[^f]*f+[^f]*', 'match');
%   collapse(matches) --> {'def' 'fghi'}
%
%
%by Gerald Dalley

if (iscell(c))
    toRemove = zeros(1,length(c));
    for i=1:length(c)
        newEntry = collapse(c{i});
        if iscell(newEntry)
            switch length(newEntry)
                case 0, 
                    toRemove(i) = 1;
                case 1, 
                    c{i} = newEntry{1};
                otherwise,
                    c{i} = newEntry;
            end
        end
    end
    c = {c{~toRemove}};
end