Add 2 images to doc

Author: james-d-mitchell

doc/m3.png

@@ -35,7 +35,7 @@ gap> IsDuplicateFree(DigraphEdges(D));
 false
 gap> IsMultiDigraph(D);
 true
-gap> D := DigraphMutableCopy(D); 
+gap> D := DigraphMutableCopy(D);
 <mutable multidigraph with 3 vertices, 7 edges>
 gap> IsMultiDigraph(D);
 true]]></Example>
@@ -233,7 +233,7 @@ false]]></Example>
   <Returns><K>true</K> or <K>false</K>.</Returns>
   <Description>
     A connected digraph is <E>biconnected</E> if it is still connected (in the
-    sense of <Ref Prop="IsConnectedDigraph"/>) when any vertex is removed. 
+    sense of <Ref Prop="IsConnectedDigraph"/>) when any vertex is removed.
       If <A>D</A> has at least 3 vertices, then <C>IsBiconnectedDigraph</C>
       implies <Ref Prop="IsBridgelessDigraph"/>;
     see <Ref Attr="ArticulationPoints"/> or <Ref Attr="Bridges"/> for a more
@@ -252,7 +252,7 @@ false]]></Example>
     the digraph.
     <P/>
 
-    See also <Ref Attr="Bridges"/>, <Ref Attr="ArticulationPoints"/>, and 
+    See also <Ref Attr="Bridges"/>, <Ref Attr="ArticulationPoints"/>, and
     <Ref Prop="IsBridgelessDigraph"/>.
     <P/>
 
@@ -504,7 +504,7 @@ true]]></Example>
       Oper="CycleDigraph"/>.<P/>
 
     A digraph is a <E>cycle</E> if and only if it is strongly connected and has
-    the same number of edges as vertices. 
+    the same number of edges as vertices.
     <P/>
 
     &MUTABLE_RECOMPUTED_PROP;
@@ -1307,14 +1307,27 @@ true
     (<Ref Prop="IsLatticeDigraph"/>) which is distributive. That is to say,
     the functions <Ref Oper="PartialOrderDigraphMeetOfVertices"/> and
     <Ref Oper="PartialOrderDigraphJoinOfVertices"/> distribute over each other.<P/>
-    
-    Equivalently, a <E>distributive lattice digraph</E> is a <E>lattice digraph</E>
+
+    Equivalently, a <E>distributive lattice digraph</E> is a lattice digraph
     in which the <E>lattice digraphs</E> representing <M>M3</M> and <M>N5</M> are
     not embeddable as lattices
     (see <URL>https://en.wikipedia.org/wiki/Distributive_lattice</URL> and
-    <Ref Prop="IsLatticeEmbedding" 
+    <Ref Oper="IsLatticeEmbedding"
     Label="for digraphs and a permutation or transformation"/>).<P/>
 
+    <Alt Only="HTML">
+        <![CDATA[
+        <figure>
+            <center>
+                <img height="200" src="m3.png"/>
+                    &nbsp;&nbsp;&nbsp;&nbsp;
+                <img height="200" src="n5.png"/>
+                <figcaption><p>The lattices <e>M3</e> and <e>N5</e>.</p></figcaption>
+            </center>
+        </figure>
+        <br/>
+        ]]>
+    </Alt>
     &MUTABLE_RECOMPUTED_PROP;
 
     <Example><![CDATA[
@@ -1342,12 +1355,25 @@ false]]></Example>
     <C>IsModularLatticeDigraph</C> returns <K>true</K> if the digraph
     <A>digraph</A> is a <E>modular lattice digraph</E>.<P/>
 
-    A <E>modular lattice digraph</E> is a <E>lattice digraph</E>
-    (<Ref Prop="IsLatticeDigraph"/>) which is modular. That is to say,
-    the <E>lattice digraph</E> representing <M>N5</M> is not
-    embeddable as a lattice
+    A <E>modular lattice digraph</E> is a lattice digraph (<Ref
+    Prop="IsLatticeDigraph"/>) which is modular. That is to say, the <E>lattice
+    digraph</E> representing <M>N5</M> is not embeddable as a lattice
     (see <URL>https://en.wikipedia.org/wiki/Modular_lattice</URL> and
-    <Ref Prop="IsLatticeEmbedding"/>). 
+    <Ref Oper="IsLatticeEmbedding"
+    Label="for digraphs and a permutation or transformation"/>).<P/>
+
+    <Alt Only="HTML">
+        <![CDATA[
+        <figure>
+            <center>
+                <img height="200" src="n5.png"/>
+
+                <figcaption><p>The lattice <e>N5</e>.</p></figcaption>
+            </center>
+        </figure>
+        <br/>
+        ]]>
+    </Alt>
 
     &MUTABLE_RECOMPUTED_PROP;
 
@@ -1468,7 +1494,7 @@ true
   <Returns><K>true</K> or <K>false</K>.</Returns>
   <Description>
     A connected digraph is <E>bridgeless</E> if it is still connected (in the
-    sense of <Ref Prop="IsConnectedDigraph"/>) when any edge is removed. 
+    sense of <Ref Prop="IsConnectedDigraph"/>) when any edge is removed.
     If <A>digraph</A> has at least 3 vertices, then <Ref
     Prop="IsBiconnectedDigraph"/> implies <C>IsBridgelessDigraph</C>;
     see <Ref Attr="ArticulationPoints"/> or <Ref Attr="Bridges"/> for a more
@@ -1487,7 +1513,7 @@ true
     the digraph.
     <P/>
 
-    See also <Ref Attr="Bridges"/>, <Ref Attr="ArticulationPoints"/>, and 
+    See also <Ref Attr="Bridges"/>, <Ref Attr="ArticulationPoints"/>, and
     <Ref Prop="IsBiconnectedDigraph"/>. <P/>
 
     &MUTABLE_RECOMPUTED_PROP;
@@ -1544,7 +1570,7 @@ true
     of <C>a</C> and <C>b</C> covers <C>b</C>.  <E>Lower semimodularity</E> is
     defined analogously. <P/>
 
-    See also <Ref Prop="IsLatticeDigraph"/>, <Ref Oper="NonUpperSemimodularPair"/>, 
+    See also <Ref Prop="IsLatticeDigraph"/>, <Ref Oper="NonUpperSemimodularPair"/>,
     and <Ref Oper="NonLowerSemimodularPair"/>.
 
     &MUTABLE_RECOMPUTED_PROP;