lib/poset: add == and hash

[nit.git] / lib / poset.nit

diff --git a/lib/poset.nit b/lib/poset.nit
index 096c128..f7d6283 100644 (file)
--- a/lib/poset.nit
+++ b/lib/poset.nit
@@ -417,6 +417,14 @@ class POSet[E]
        #
        # assert pos2["B"].direct_greaters.has_exactly(["D", "Y"])
        # ~~~
+       #
+       # If the `elements` contains all then the result is a clone of self.
+       #
+       # ~~~
+       # var pos3 = pos.sub(pos)
+       # assert pos3 == pos
+       # assert pos3 == pos.clone
+       # ~~~
        fun sub(elements: Collection[E]): POSet[E]
        do
                var res = new POSet[E]
@@ -432,6 +440,50 @@ class POSet[E]
                end
                return res
        end
+
+       # Two posets are equal if they contain the same elements and edges.
+       #
+       # ~~~
+       # var pos1 = new POSet[String]
+       # pos1.add_chain(["A", "B", "C", "D", "E"])
+       # pos1.add_chain(["A", "X", "C", "Y", "E"])
+       #
+       # var pos2 = new POSet[Object]
+       # pos2.add_edge("Y", "E")
+       # pos2.add_chain(["A", "X", "C", "D", "E"])
+       # pos2.add_chain(["A", "B", "C", "Y"])
+       #
+       # assert pos1 == pos2
+       #
+       # pos1.add_edge("D", "Y")
+       # assert pos1 != pos2
+       #
+       # pos2.add_edge("D", "Y")
+       # assert pos1 == pos2
+       #
+       # pos1.add_node("Z")
+       # assert pos1 != pos2
+       # ~~~
+       redef fun ==(other) do
+               if not other isa POSet[nullable Object] then return false
+               if not self.elements.keys.has_exactly(other.elements.keys) then return false
+               for e, ee in elements do
+                       if ee.direct_greaters != other[e].direct_greaters then return false
+               end
+               assert hash == other.hash
+               return true
+       end
+
+       redef fun hash
+       do
+               var res = 0
+               for e, ee in elements do
+                       if e == null then continue
+                       res += e.hash
+                       res += ee.direct_greaters.length
+               end
+               return res
+       end
 end
 
 # View of an objet in a poset