+proc forward_pass {id children} {
+ global idtags desc_tags idheads desc_heads alldtags tagisdesc
+
+ set dtags {}
+ set dheads {}
+ foreach child $children {
+ if {[info exists idtags($child)]} {
+ set ctags [list $child]
+ } else {
+ set ctags $desc_tags($child)
+ }
+ if {$dtags eq {}} {
+ set dtags $ctags
+ } elseif {$ctags ne $dtags} {
+ set dtags [combine_dtags $dtags $ctags]
+ }
+ set cheads $desc_heads($child)
+ if {$dheads eq {}} {
+ set dheads $cheads
+ } elseif {$cheads ne $dheads} {
+ set dheads [lsort -unique [concat $dheads $cheads]]
+ }
+ }
+ set desc_tags($id) $dtags
+ if {[info exists idtags($id)]} {
+ set adt $dtags
+ foreach tag $dtags {
+ set adt [concat $adt $alldtags($tag)]
+ }
+ set adt [lsort -unique $adt]
+ set alldtags($id) $adt
+ foreach tag $adt {
+ set tagisdesc($id,$tag) -1
+ set tagisdesc($tag,$id) 1
+ }
+ }
+ if {[info exists idheads($id)]} {
+ lappend dheads $id
+ }
+ set desc_heads($id) $dheads
+}
+