Hi. APL2 Programming Language Reference, p. 188 says: (0≠L)/R ←→ ⊃,/L⊂R
However, GNU APL gives different results when 0=↑L :
L←1 0 1 0 ◊ R←'abcd'
(⎕← (0≠L)/R )≡(⎕← ⊃,/L⊂R )
ac
ac
1
L←1 1 1 0 ◊ R←'abcd'
(⎕← (0≠L)/R )≡(⎕← ⊃,/L⊂R )
abcd
abc
0
L←0 0 1 0 ◊ R←'abcd'
(⎕← (0≠L)/R )≡(⎕← ⊃,/L⊂R )
DOMAIN ERROR
(⎕←(0≠L)/R)≡(⎕←⊃,/L⊂R)
^ ^
Hudson
