Convert list of separated numerical numbers to strings

Problem: given a list of numbers such as

{{1, 2}, 
 {5, 3, 7}, 
 {4} 
 }

convert the above to list of strings

{"12", 
 "537", 
 "4"}

Mathematica

a={{1,2},{5,3,7},{4}}; 
Map[ToString[#]&,a,{2}]; 
Map[StringJoin[#]&,%]

List["12","537","4"]

Matlab

a={[1,2],[5,3,7],[4]}; 
r=arrayfun(@(i) ... 
   cellstr(num2str(a{i})),1:length(a)); 
r'

ans = 
    '1  2' 
    '5  3  7' 
    '4'

answer below is due to Bruno Luong at Matlab newsgroup

a={[1,2],[5,3,7],[4]}; 
map='0':'9'; 
cellfun(@(x) map(x+1), a, 'uni', 0)

    '12'    '537'    '4'

Maple

a:=[[1,2],[5,3,7],[4]]; 
map(x->convert(cat(op(x)), string),a);

["12", "537", "4"]