Until now everything was not too complicated. 3 was first in Python, then in J.

1
echo +/|-//:~"1'a b'=:|:>".&.>cutLF CR-.~fread'01.dat'
echo +/a*+/"1 a=/b
2
f=: [:(([:*./1 2 3 e.~])+.[:*./_1 _2 _3 e.~])2-/\]
g=: f+.[:+./f"1&(]({~<&<&<)~"0 1~[:i.#) NB. should have used _1]\ instead ( Read more... )