1 # This file is part of NIT ( http://www.nitlanguage.org ).
3 # Copyright 2012 Jean Privat <jean@pryen.org>
5 # Licensed under the Apache License, Version 2.0 (the "License");
6 # you may not use this file except in compliance with the License.
7 # You may obtain a copy of the License at
9 # http://www.apache.org/licenses/LICENSE-2.0
11 # Unless required by applicable law or agreed to in writing, software
12 # distributed under the License is distributed on an "AS IS" BASIS,
13 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 # See the License for the specific language governing permissions and
15 # limitations under the License.
17 # Pre order sets and partial order set (ie hierarchies)
21 # This class modelize an incremental preorder graph where new node and edges can be added (but no removal)
22 # Preorder graph has two caracteristics:
23 # * reflexivity: an element is in relation with itself (ie `self.has(e) implies self.has_edge(e,e)`)
24 # * transitivity: `(self.has_edge(e,f) and self.has_edge(f,g)) implies self.has_edge(e,g)`
25 class POSet[E
: Object]
29 redef fun iterator
do return elements
.keys
.iterator
32 private var elements
: HashMap[E
, POSetElement[E
]] = new HashMap[E
, POSetElement[E
]]
34 redef fun has
(e
) do return self.elements
.keys
.has
(e
)
36 # Add a node (an element) to the posed
37 # The new element is added unconnected to any other nodes (it is both a new root and a new leaf).
38 # Return the POSetElement associated to `e`.
39 # If `e` is already present in the POSet then just return the POSetElement (usually you will prefer []) is this case.
40 fun add_node
(e
: E
): POSetElement[E
]
42 if elements
.keys
.has
(e
) then return self.elements
[e
]
43 var poe
= new POSetElement[E
](self, e
, elements
.length
)
46 self.elements
[e
] = poe
50 # Return a view of `e` in the poset.
51 # This allows to asks manipulate elements in thier relation with others elements.
53 # var poset: POSet[Something] # ...
55 # for y in poset[x].direct_greaters do
61 fun [](e
: E
): POSetElement[E
]
63 assert elements
.keys
.has
(e
)
64 return self.elements
[e
]
67 # Add an edge from `f` to `t`.
68 # Because a POSet is transitive, all transitive edges are also added to the graph.
69 # If the edge already exists, the this function does nothing.
70 # If a reverse edge (from `t` to `f`) already exists, a loop is created.
72 # FIXME: Do somethind clever to manage loops.
77 # Skip if edge already present
78 if fe
.tos
.has
(t
) then return
79 # Add the edge and close the transitivity
81 var ffe
= self.elements
[ff
]
83 var tte
= self.elements
[tt
]
88 # Update the transitive reduction
89 if te
.tos
.has
(f
) then return # Skip the reduction if there is a loop
91 for x
in te
.dfroms
.to_a
do
92 var xe
= self.elements
[x
]
98 for x
in fe
.dtos
.to_a
do
99 var xe
= self.elements
[x
]
100 if xe
.froms
.has
(t
) then
109 # Is there an edge (transitive or not) from `f` to `t`?
110 # Since the POSet is reflexive, true is returned if `f == t`.
111 fun has_edge
(f
,t
: E
): Bool
113 if not elements
.keys
.has
(f
) then return false
114 var fe
= self.elements
[f
]
118 # Is there a direct edge from `f` to `t`?
119 # Note that because of loops, the result may not be the expected one.
120 fun has_direct_edge
(f
,t
: E
): Bool
122 if not elements
.keys
.has
(f
) then return false
123 var fe
= self.elements
[f
]
124 return fe
.dtos
.has
(t
)
127 # Display the POSet in a gaphical windows.
128 # Graphviz with a working -Txlib is expected.
132 var f
= new OProcess("dot", "-Txlib")
134 f
.write
"digraph \{\n"
135 for x
in elements
.keys
do
137 var xe
= self.elements
[x
]
139 if self.has_edge
(y
,x
) then
140 f
.write
"\"{x}\
" -> \"{y}\
"[dir=both];\n"
142 f
.write
"\"{x}\
" -> \"{y}\
";\n"
151 # Compare two elements in an arbitrary total order.
152 # Tis function is mainly used to sort elements of the set in an arbitrary linear extension.
153 # if a<b then return -1
154 # if a>b then return 1
155 # if a == b then return 0
156 # else return -1 or 1
157 # The total order is stable unless a new node or a new edge is added
158 redef fun compare
(a
, b
: E
): Int
160 var ae
= self.elements
[a
]
161 var be
= self.elements
[b
]
162 var res
= ae
.tos
.length
<=> be
.tos
.length
163 if res
!= 0 then return res
164 return elements
[a
].count
<=> elements
[b
].count
167 # Sort a sorted array of poset elements using linearization order
168 fun linearize
(elements
: Collection[E
]): Array[E
] do
169 var lin
= elements
.to_a
175 # View of an objet in a poset
176 # This class is a helper to handle specific queries on a same object
178 # For instance, one common usage is to add a specific attribute for each poset a class belong.
181 # var in_some_relation: POSetElement[Thing]
182 # var in_other_relation: POSetElement[Thing]
185 # t.in_some_relation.greaters
187 class POSetElement[E
: Object]
188 # The poset self belong to
191 # The real object behind the view
194 private var tos
= new HashSet[E
]
195 private var froms
= new HashSet[E
]
196 private var dtos
= new HashSet[E
]
197 private var dfroms
= new HashSet[E
]
200 # This attribute is used to force a total order for POSet#compare
201 private var count
: Int
203 # Return the set of all elements `t` that have an edge from `element` to `t`.
204 # Since the POSet is reflexive, element is included in the set.
205 fun greaters
: Collection[E
]
210 # Return the set of all elements `t` that have a direct edge from `element` to `t`.
211 fun direct_greaters
: Collection[E
]
216 # Return the set of all elements `f` that have an edge from `f` to `element`.
217 # Since the POSet is reflexive, element is included in the set.
218 fun smallers
: Collection[E
]
223 # Return the set of all elements `f` that have an edge from `f` to `element`.
224 fun direct_smallers
: Collection[E
]
229 # Is there an edge from `element` to `t`?
232 return self.tos
.has
(t
)
235 # Is `t != element` and is there an edge from `element` to `t`?
238 return t
!= self.element
and self.tos
.has
(t
)
241 # The length of the shortest path to the root of the poset hierarchy
243 if direct_greaters
.is_empty
then
247 for p
in direct_greaters
do
248 var d
= poset
[p
].depth
+ 1
249 if min
== -1 or d
< min
then