Add UnitEdgeWeightedDigraph (#886)

* Add unitedgeweight digraph

* Add 'edge-weighted' output to tests

* gaplint checks implemented

* fix trailing whitespace at line:86

* Make UnitEdgeWeightedDigraph more concise

---------

Co-authored-by: Michael Young <mct25@st-andrews.ac.uk>

Author: coraaked

gap/weights.gd

@@ -14,6 +14,7 @@ DeclareGlobalFunction("EdgeWeightedDigraph");
 DeclareProperty("IsNegativeEdgeWeightedDigraph", IsDigraph and HasEdgeWeights);
 DeclareAttribute("EdgeWeightedDigraphTotalWeight",
 IsDigraph and HasEdgeWeights);
+DeclareAttribute("UnitEdgeWeightedDigraph", IsDigraph);
 
 # 2. Edge Weight Copies
 DeclareOperation("EdgeWeightsMutableCopy", [IsDigraph and HasEdgeWeights]);

gap/weights.gi

@@ -79,6 +79,11 @@ InstallMethod(EdgeWeightedDigraphTotalWeight,
 [IsDigraph and HasEdgeWeights],
 D -> Sum(EdgeWeights(D), Sum));
 
+InstallMethod(UnitEdgeWeightedDigraph, "for a digraph",
+[IsDigraph],
+D -> EdgeWeightedDigraph(D, List(OutNeighbours(D),
+                                 l -> ListWithIdenticalEntries(Length(l), 1))));
+
 #############################################################################
 # 2. Copies of edge weights
 #############################################################################

tst/testinstall.tst

@@ -541,6 +541,24 @@ gap> AutomorphismGroup(D)
 > = Group([(1, 2, 3), (1, 2), (4, 5, 6), (4, 5), (1, 4)(2, 5)(3, 6)]);
 true
 
+# UnitEdgeWeightedDigraph
+gap> D := UnitEdgeWeightedDigraph(Digraph([[2], [1, 3], [1]]));
+<immutable edge-weighted digraph with 3 vertices, 4 edges>
+gap> EdgeWeights(D);
+[ [ 1 ], [ 1, 1 ], [ 1 ] ]
+gap> D := UnitEdgeWeightedDigraph(Digraph([[3, 4], [1, 3, 4], [2, 4], [1, 2, 3]]));
+<immutable edge-weighted digraph with 4 vertices, 10 edges>
+gap> EdgeWeights(D);
+[ [ 1, 1 ], [ 1, 1, 1 ], [ 1, 1 ], [ 1, 1, 1 ] ]
+gap> D := UnitEdgeWeightedDigraph(EmptyDigraph(4));
+<immutable empty edge-weighted digraph with 4 vertices>
+gap> EdgeWeights(D);
+[ [  ], [  ], [  ], [  ] ]
+gap> D := UnitEdgeWeightedDigraph(EdgeWeightedDigraph([[2], []], [[5], []]));
+<immutable edge-weighted digraph with 2 vertices, 1 edge>
+gap> EdgeWeights(D);
+[ [ 1 ], [  ] ]
+
 # SwapDigraphs
 gap> C := Digraph(IsMutableDigraph, [[4], [5], [1, 2], [], []]);;
 gap> D := Digraph(IsMutableDigraph, [[2, 3, 4], [1, 3, 4, 5], [1, 2], [5], [4]]);;