Epsilon ∊
Monadic Epsilon means
If ⎕ML=0
Type Of
∊ 3 3⍴1 'abc'
0 0
0
0 0
If ⎕ML≥1
Enlist
mat
1 2 3
4 5 6
∊ 0 mat (7 8) 9
0 1 2 3 4 5 6 7 8 9
∊ 2 3⍴1 'abc'
1 abc 1 abc 1 abc
Dyadic Epsilon means
'abc' 4 ∊ 4 'ab' 'abcd'
0 1
mat ∊ 6 2 7 4
0 1 0
1 0 1