USING: help sequences ;

HELP: flatten "( seq -- seq)"
{ $values { "obj" "an object" } { "seq" "a new sequence" } }
{ $description "Recursively descends into lists, arrays, vectors and wrappers. Leaf elements are collected into a new sequence which is output at the end of the traversal." }
{ $notes "This word does not descend into virtual sequences, or user-defined sequences." } ;