diff example of 2 directories

gistfile1.txt

~/tmp 𝜵 ls 3 4
3:
1  10  2  4  5  6  7  8  9  a  b  d

4:
1  10  2  3  5  6  7  8  9  c
~/tmp 𝜵 diff -y <(ls 3) <(ls 4)
1                                                               1
10                                                              10
2                                                               2
4                                                             | 3
5                                                               5
6                                                               6
7                                                               7
8                                                               8
9                                                               9
a                                                             | c
b                                                             <
d                                                             <