someone on the chat was asking for a topological sort algorithm. Here's one I have lying around, for what it's worth.

# [TopologicalSort] takes an alternative (which is represented by a directed acyclic graph, DAG) # and returns a topological sort of it. A topological sort of a DAG is # a list of all the vertices of the DAG (here a list of package names), # such that if A -> B is in the DAG, then the index of A in the list is # less than the index of B in the list. In addition, when constructing # the list, this proc includes the corresponding requirement along with # each package name. Thus, the result is a requirement list, ordered so # that each requirement is listed after its prerequisites. # # proc ::package::TopologicalSort alt { proc TopologicalSort alt { # Unpack the alternative data structure lassign $alt DAG MAP array set dag [lindex $DAG 0] set max [lindex $DAG 1] array set map $MAP set answer {} foreach vertex $max { unset dag($vertex) } while {[llength $max]} { set pkg [lindex $max 0] set max [lrange $max 1 end] set answer [linsert $answer 0 [ linsert [lindex $map($pkg) 1] 0 $pkg]] foreach vertex [array names dag] { set idx [lsearch -exact $dag($vertex) $pkg] set dag($vertex) [lreplace $dag($vertex) $idx $idx] if {[llength $dag($vertex)] == 0} { lappend max $vertex unset dag($vertex) } } } set answer } # Test: catch {console show} set Result {} lappend Topo foo 1 bar 2 puts "Topo: $Topo" set Result [ TopologicalSort $Topo ] puts $Result

The above code may make little sense out of its context. For that, see [L1 ]. Look in **mkdepend.tcl**.

HJG: An example with some data would be nice. The above test gives an error "list must have an even number of elements..."