Deduplicate some functions

Author: james-d-mitchell

gap/dot.gd

@@ -1,17 +1,17 @@
 #! @Chapter
 #! @ChapterTitle An introduction to the DOT language and Graphviz.
-#! This chapter explains what the DOT and graphviz are, 
+#! This chapter explains what the DOT and graphviz are,
 #! key basic concepts relating to them, and how this package interacts with them.
 
 #! @Section A Brief Introduction
-#! DOT is a language for descrbing to a computer how to display a visualization 
-#! for a graph or digraph. Graphviz is a graph vizualization software which can 
+#! DOT is a language for descrbing to a computer how to display a visualization
+#! for a graph or digraph. Graphviz is a graph vizualization software which can
 #! consume DOT and produce vizual outputs. This package is designed to allow
-#! users to programmatically construct objects in GAP which can then be 
+#! users to programmatically construct objects in GAP which can then be
 #! converted into DOT. That DOT can then be inputted into the graphviz software
-#! to produce a visual output. As DOT is central to the design of this package 
+#! to produce a visual output. As DOT is central to the design of this package
 #! it will likely be helpful to have a basic understanding of the language.
-#! For more information about DOT see 
+#! For more information about DOT see
 #! <URL>https://graphviz.org/doc/info/lang.html</URL>.
 
 #! @Chapter
@@ -20,13 +20,15 @@
 #! @Section Graphviz Categories
 
 #! @BeginGroup Filters
-#! @Description Every object in graphviz belongs to the IsGVObject category. 
-#! The categories following it are for further specificity on the type of 
+#! @Description Every object in graphviz belongs to the IsGVObject category.
+#! The categories following it are for further specificity on the type of
 #! objects. These are graphs, digraphs, nodes and edges respectively.
 #! All are direct subcategories of IsGVObject excluding IsGVDigraph which is a
-#! subcategory of is GVGraph. 
+#! subcategory of is GVGraph.
 DeclareCategory("IsGVObject", IsObject);
 DeclareCategory("IsGVGraph", IsGVObject);
+# TODO change to IsGVObject below, since digraphs aren't a special kind of
+# graph, unless I'm (JDM) mistaken?
 DeclareCategory("IsGVDigraph", IsGVGraph);
 DeclareCategory("IsGVContext", IsGVGraph);
 DeclareCategory("IsGVNode", IsGVObject);
@@ -54,10 +56,10 @@ DeclareOperation("GraphvizDigraph", []);
 #! @EndGroup
 
 #! @Section Get Operations
-#! This section covers the operations for getting information about graphviz 
+#! This section covers the operations for getting information about graphviz
 #! objects.
 
-#! @Subsection For all graphviz objects. 
+#! @Subsection For all graphviz objects.
 
 #! @Arguments obj
 #! @Returns the name of the provided graphviz object
@@ -85,10 +87,10 @@ DeclareOperation("GraphvizGetSubgraph", [IsGVGraph, IsObject]);
 
 #! @Arguments graph, name
 #! @Returns a graph with the provided name.
-#! @Description 
+#! @Description
 #! Searches through the tree of subgraphs connected to this subgraph for a graph
-#! with the provided name. 
-#! It returns the graph if it exists. 
+#! with the provided name.
+#! It returns the graph if it exists.
 #! If no such graph exists then it will return fail.
 DeclareOperation("GraphvizFindGraph", [IsGVGraph, IsObject]);
 
@@ -157,15 +159,15 @@ DeclareOperation("GraphvizFilterEdges", [IsGVGraph, IsFunction]);
 
 #! @Arguments graph, head_name, tail_name
 #! @Returns the modified graph.
-#! @Description Filters the graph's edges, removing edges between nodes with 
+#! @Description Filters the graph's edges, removing edges between nodes with
 #! the specified names.
 DeclareOperation("GraphvizFilterEnds", [IsGVGraph, IsObject, IsObject]);
 
 #! @Subsection For modifying object attributes.
 
 #! @Arguments obj, attrs
 #! @Returns the modified object.
-#! @Description 
+#! @Description
 #!    Updates the attribtues of the object.
 #!    All current attributes remain.
 #!    If an attribute already exists and a new value is provided, the old value
@@ -176,15 +178,15 @@ DeclareOperation("GraphvizSetAttr", [IsGVObject, IsObject]);
 
 #! @Arguments obj, label
 #! @Returns the modified object.
-#! @Description 
+#! @Description
 #!    Updates the label of the object.
-#!    If a label already exists and a new value is provided, the old value will 
+#!    If a label already exists and a new value is provided, the old value will
 #!    be overwritten.
 DeclareOperation("GraphvizSetLabel", [IsGVObject, IsObject]);
 
 #! @Arguments obj, color
 #! @Returns the modified object.
-#! @Description 
+#! @Description
 #!    Updates the color of the object.
 #!    If a color already exists and a new value is provided, the old value will
 #!    be overwritten.

gap/dot.gi

@@ -10,8 +10,6 @@ DeclareOperation("GV_StringifyGraphHead", [IsGVGraph]);
 DeclareOperation("GV_StringifyDigraphHead", [IsGVGraph]);
 DeclareOperation("GV_StringifySubgraphHead", [IsGVGraph]);
 DeclareOperation("GV_StringifyContextHead", [IsGVGraph]);
-DeclareOperation("GV_StringifyGraphEdge", [IsGVEdge]);
-DeclareOperation("GV_StringifyDigraphEdge", [IsGVEdge]);
 DeclareOperation("GV_StringifyNode", [IsGVNode]);
 DeclareOperation("GV_StringifyGraphAttrs", [IsGVGraph]);
 DeclareOperation("GV_StringifyNodeEdgeAttrs", [IsGV_Map]);
@@ -375,50 +373,21 @@ end);
 
 InstallMethod(ViewString, "for a graphviz graph", [IsGVGraph],
 function(g)
-  local result, edges, nodes;
-  result := "";
-  edges  := Length(GraphvizEdges(g));
-  nodes  := Length(GV_MapNames(GraphvizNodes(g)));
-
-  Append(result, StringFormatted("<graphviz graph ", GraphvizName(g)));
-
-  if GraphvizName(g) <> "" then
-    Append(result, StringFormatted("{} ", GraphvizName(g)));
-  fi;
-
-  Append(result, StringFormatted("with {} ", GV_Pluralize(nodes, "node")));
-  Append(result, StringFormatted("and {}>", GV_Pluralize(edges, "edge")));
+  local result, edges, nodes, kind;
 
-  return result;
-end);
-
-InstallMethod(ViewString, "for a graphviz digraph", [IsGVDigraph],
-function(g)
-  local result, edges, nodes;
   result := "";
   edges  := Length(GraphvizEdges(g));
   nodes  := Length(GV_MapNames(GraphvizNodes(g)));
 
-  Append(result, StringFormatted("<graphviz digraph ", GraphvizName(g)));
-
-  if GraphvizName(g) <> "" then
-    Append(result, StringFormatted("{} ", GraphvizName(g)));
+  if IsGVDigraph(g) then
+    kind := "digraph";
+  elif IsGVContext(g) then
+    kind := "context";
+  else
+    kind := "graph";
   fi;
 
-  Append(result, StringFormatted("with {} ", GV_Pluralize(nodes, "node")));
-  Append(result, StringFormatted("and {}>", GV_Pluralize(edges, "edge")));
-
-  return result;
-end);
-
-InstallMethod(ViewString, "for a graphviz context", [IsGVContext],
-function(g)
-  local result, edges, nodes;
-  result := "";
-  edges  := Length(GraphvizEdges(g));
-  nodes  := Length(GV_MapNames(GraphvizNodes(g)));
-
-  Append(result, StringFormatted("<graphviz context ", GraphvizName(g)));
+  Append(result, StringFormatted("<graphviz {} ", kind));
 
   if GraphvizName(g) <> "" then
     Append(result, StringFormatted("{} ", GraphvizName(g)));
@@ -430,9 +399,9 @@ function(g)
   return result;
 end);
 
-# ###########################################################
+############################################################
 # Getters
-# ###########################################################
+############################################################
 InstallMethod(GraphvizName,
 "for a graphviz object",
 [IsGVObject],
@@ -1059,33 +1028,19 @@ function(node)
 end);
 
 # @ Return DOT graph edge statement line.
-InstallMethod(GV_StringifyGraphEdge, "for a graphviz edge",
-[IsGVEdge],
-function(edge)
-  local head, tail, attrs;
-  head  := GraphvizName(GraphvizHead(edge));
-  tail  := GraphvizName(GraphvizTail(edge));
-  attrs := GraphvizAttrs(edge);
-
-  # handle : syntax
-  return StringFormatted("\t{} -- {}{}\n",
-                         head,
-                         tail,
-                         GV_StringifyNodeEdgeAttrs(attrs));
-end);
-
-# @ Return DOT digraph edge statement line.
-InstallMethod(GV_StringifyDigraphEdge, "for a graphviz edge",
-[IsGVEdge],
-function(edge)
+BindGlobal("GV_StringifyEdge",
+function(edge, edge_str)
   local head, tail, attrs;
+  Assert(0, IsGVEdge(edge));
+  Assert(0, IsString(edge_str));
   head  := GraphvizName(GraphvizHead(edge));
   tail  := GraphvizName(GraphvizTail(edge));
   attrs := GraphvizAttrs(edge);
 
   # handle : syntax
-  return StringFormatted("\t{} -> {}{}\n",
+  return StringFormatted("\t{} {} {}{}\n",
                          head,
+                         edge_str,
                          tail,
                          GV_StringifyNodeEdgeAttrs(attrs));
 end);
@@ -1233,9 +1188,9 @@ function(graph, is_subgraph)
       Append(result, GV_StringifyNode(obj));
     elif IsGVEdge(obj) then
       if IsGVDigraph(GV_GetRoot(graph)) then
-        Append(result, GV_StringifyDigraphEdge(obj));
+        Append(result, GV_StringifyEdge(obj, "->"));
       else
-        Append(result, GV_StringifyGraphEdge(obj));
+        Append(result, GV_StringifyEdge(obj, "--"));
       fi;
     else
       return ErrorNoReturn("Invalid graphviz object type.");