|L and R are arbitrary arrays.|
|Z is an array of rank 0⌈1+(⍴⍴R)-⍴⍴L and shape (1-⍴⍴L)↓⍴R.|
|For matrices, the result is equivalent to (⊂ L)⍳⊂ R (lookup the rows of one array in another) which encapsulates a common idiom in one symbol.|
|For higher rank arrays, the arguments are enclosed to become vectors of subarrays and then the usual lookup produces the final result.|
|This function is sensitive to both ⎕IO and ⎕CT.|
For example, in origin-1
⎕←L←6 4⍴'DinaDickJohnJaneSue Mary Dina Dick John Jane Sue Mary ⎕←R←3 4⍴'JaneBob Sue '
Jane Bob Sue L⍸R 4 7 5
This function was suggested by the language designers of Dyalog APL.