Better idea for double list comprehension?

[CJS]

I'm trying to write a D function that does the same as this 
Python function:

def cross(A, B):
    "Cross product of elements in A and elements in B."
    return [a+b for a in A for b in B]
where A and B are strings. (So cross("ab","12") is ["a1", "b1", 
"a2", "b2"]).

It's easy to get something that works the same in D, but I'd like 
to make it as simple and short as possible. The best I could come 
up with is


string[] cross(string A, string B){
    string[] grid;
    foreach(t; cartesianProduct(A,B)){
        grid ~= (to!string(p[0]) ~ to!string(p[1]));