fail

fail, keyword

The keyword fail prevents Envision from replacing an empty selection by a default value.

It applies to lookups:

table T[x] = with
  [| "aa" as X, 11 as Y|]
  [| "bb", 12 |]
  [| "cc", 13 |]

a = T.Y["bb"] default fail

show scalar "" with a // displays 12