Up Arrow ↑
Monadic Up Arrow means
If ⎕ML<2 Mix
↑ 'Hip' 'Hop'
Hip
Hop
↑ (6 4) 5 3
6 4
5 0
3 0
↑[0.5] 'Hip' 'Hop'
HH
io
pp
If ⎕ML≥2 First
↑ (6 4) 5 3
6 4
Dyadic Up Arrow means
4 ↑ 'Pineapple'
Pine
¯5 ↑ 'Pineapple'
apple
mat
1 2 3 4
5 6 7 8
9 10 11 12
2 ¯3 ↑ mat
2 3 4
6 7 8
¯2 ↑ mat
5 6 7 8
9 10 11 12
¯2 3 ↑ 7
0 0 0
7 0 0