: if-empty ( ..a seq quot1: ( ..a -- ..b ) quot2: ( ..a seq -- ..b ) -- ..b )
[ dup empty? ] [ [ drop ] prepose ] [ ] tri* if ; inline
-: when-empty ( ... seq quot: ( ... -- obj ) -- ... seq/obj ) [ ] if-empty ; inline
+: when-empty ( ... seq quot: ( ... -- ... obj ) -- ... seq/obj ) [ ] if-empty ; inline
: unless-empty ( ... seq quot: ( ... seq -- ... ) -- ... ) [ ] swap if-empty ; inline
: delete-all ( seq -- ) 0 swap set-length ;