[Bug-apl] ERR function in APL2?

[Elias Mårtenson]

I was browsing the APL2 documentation, and came across the following code (page 56, on the PDF here):

[0]  Z←NAME GETW N

[1] ⍝ GET ITEMS N FROM THE TABLE NAMED NAME

[2]  Z←''

[3]  →('NOT A VALID TABLE NAME' ERR~(⊂NAME)∊TABLES)/0

[4]  TAB←⍎NAME

[5]  B←N∊TAB[;1]

[6]  →0ρ('ITEM(S)'((~B)/N)'NOT FOUND')ERR~^/B

[7]  →(~∨/B)/0  ⍝ EXIT IF NONE FOUND

[8]  Z←(TAB[;1]∊N)⌿›TAB

What is ERR here?  It seems like a function that sets some error state? It certainly looks like something useful to have. I can't think of any way I could build this myself though.

Regards,

Elias