# joins an array of string into a single string, with, optionally,
# a separator specified as second argument.
#                                      cd, 2008

ConcatStrings := proc(a_:array({string,numeric});(b=''):string)
    if length(a_) = 0 then return(''); fi;
    a := copy(a_); for i to length(a) do a[i] := string(a[i]) od;
    n := length(a);
    lb := length(b);
    res := CreateString(sum(zip(length(a)))+(n-1)*lb);
    cur := 1;
    for i to n do
        for j to length(a[i]) do
            res[cur] := a[i,j];
            cur := cur+1;
        od;
        if i < n then
            for j to lb do
                res[cur] := b[j];
                cur := cur+1;
            od;
        fi;
    od;
    return(res);
end: