To reduce the boilerplate of checking if a sequence is empty, several combinators are provided.

Checking if a sequence is empty:

if-empty ( ..a seq quot1: ( ..a -- ..b ) quot2: ( ..a seq -- ..b ) -- ..b )

when-empty ( ... seq quot: ( ... -- ... obj ) -- ... seq/obj )

unless-empty ( ... seq quot: ( ... seq -- ... ) -- ... )