Identity element for
∘.
,
?
The identity element of
,
is the empty list
⍬
:
⍬
,
3
2
1
,
⍬
3 2 1
But that's not the identity element of
∘.
,
:
⍬
∘.
,
3
2
1
⍝ APL keeps not printing anything!
The identity element of an outer product needs to be an array whose shape is the empty list!
⍴
⍬
0