tree_level

tree_level   tree   n   { result "" }

returns the n-th level of a tree (where 0 is the root tree) as a list of trees

Source code:

    if { [empty_string_p $tree] } { return $result }
    if { $n==0 } {
	lappend result $tree
    } else {
	foreach subtree [tail $tree] {
	    set result [tree_level $subtree [expr $n-1] $result]
	}
    }
    return $result