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
foreach {DAG MAP} $alt {break}
array set dag [lindex $DAG 0]
set max [lindex $DAG 1]
array set map $MAP
set answer [list]
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 $ResultThe 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..."