fix ES.10

CppCoreGuidelines.md

@@ -9315,9 +9315,15 @@ or:
     // better: base * pow(FLT_RADIX, exponent); FLT_RADIX is usually 2
     double scalbn(double base, int exponent);
 
+##### Example
+
+    int a=7, b=9, c, d=10, e=3;
+
+In a long list of declarators is is easy to overlook an uninitializeed variable.
+
 ##### Enforcement
 
-Flag non-function arguments with multiple declarators involving declarator operators (e.g., `int* p, q;`)
+Flag variable and constant declarations with multiple declarators (e.g., `int* p, q;`)
 
 ### <a name="Res-auto"></a>ES.11: Use `auto` to avoid redundant repetition of type names
 

dump.cpp

@@ -0,0 +1,230 @@
+// Ah... The joys graph data structures :)
+// A hole into which many a good computer scientist has fallen, never to be heard from again.
+//					- Andrew Sutton
+
+/*
+	Basic idea: provide concepts that define the interface(s) to different kinds of graphs so that you can do
+	basic graph operations and algoriths without knowing exactly which kind of graph it is and keep ignorant
+	about implementation details.
+    
+    Basic design idea: do like the STL
+*/
+
+/*
+// Graph concepts (like STL containers):
+// Do we need them (STL doesn't make containers explicit)
+template<class G> concept bool Graph = false; // general graph operations
+template<class G> concept bool DAG = false;	 // operations simplified for DAGs (any extra operations?)
+template<class G> concept bool Tree = false;	 // operations simplified for trees (any extra operations?)
+
+// accessor concepts (like STL Iterators):
+template<class G> concept bool Edge_ref = false;	     // most general and slowest
+template<class G> concept bool DAG_edge_ref = false;	 // operations simplified for DAGs (any extra operations?)
+template<class G> concept bool Tree_edge_ref = false; // operations simplified for trees (any extra operations?)
+
+template<class G> concept bool Vertex_ref = false;      // most general and slowest
+template<class G> concept bool DAG_vertex_ref = false;  // operations simplified for DAGs (any extra operations?)
+template<class G> concept bool Tree_vertex_ref = false; // operations simplified for DAGs (any extra operations?)
+
+// the value type (in a more general design, this would be a template parmeter):
+struct Val {};
+
+// specific directed graphs:
+struct Tree {};
+struct Dag { };
+struct Dgraph {};
+
+struct Node_ref {};
+struct Edge_ref {};	// Is an Edge an object? (if not, refer to parent node)
+
+struct DAG_vertex_ref {};
+struct DAG_edge_ref {};	// Is an Edge an object? (if not, refer to parent node)
+
+struct Gnode_ref {};
+struct Gedge_ref {};	// Is an Edge an object? (if not, refer to parent node)
+
+// another Graph representation:
+struct DGN_ref {};
+struct DGE_ref {};	// Is an Edge an object? (if not, refer to parent node)
+
+// use:
+template<Graph G>
+void traverse(G& g)
+{
+	vector<???> found;	// there is a way (look up traits), lets try g::value_type
+}
+
+*/
+
+/*
+	Basic idea: provide concepts that define the interface(s) to different kinds of graphs so that you can do
+	basic graph operations and algoriths without knowing exactly which kind of graph it is and keep ignorant
+	about implementation details.
+    
+    Basic design idea: do like the STL
+*/
+
+/*
+// Graph concepts (like STL containers):
+// Do we need them (STL doesn't make containers explicit)
+template<class G> concept bool Graph =  // general graph operations
+	requires { typename G::value_type; };
+template<class G> concept bool DAG = Graph<G> && requires(G g) { tops(g); };	 // operations simplified for DAGs 
+template<class G> concept bool Tree = DAG<G> && requires(G g) { top(g); };	 // operations simplified for trees
+
+// accessor concepts (like STL Iterators):
+template<class E> concept bool Edge_ref =      // most general and slowest
+	requires { typename E::value_type; };
+template<class E> concept bool DAG_edge_ref = // operations simplified for DAGs (any extra operations?)
+	Edge_ref<E> && false;	 
+template<class E> concept bool Tree_edge_ref = // operations simplified for trees (any extra operations?)
+	DAG_edge_ref<E> && false; 
+
+template<class G> concept bool Vertex_ref = true;      // most general and slowest
+template<class G> concept bool DAG_vertex_ref = false;  // operations simplified for DAGs (any extra operations?)
+template<class G> concept bool Tree_vertex_ref = false; // operations simplified for DAGs (any extra operations?)
+
+// the value type (in a more general design, this would be a template parmeter):
+struct Val {};
+
+// specific directed graphs (note: we can't assume common structure or common naming from implementation):
+struct Tree {
+  	using value_type = Val;
+};
+
+struct Node_ref {};
+struct Edge_ref {};	// Is an Edge an object? (if not, refer to parent node)
+
+void tops(Tree&);	// return vector Tree_vertex_refs
+Node_ref top(Tree&);
+
+struct Dag {
+  	using value_type = Val;
+};
+
+struct DAG_vertex_ref {};
+struct DAG_edge_ref {};	// Is an Edge an object? (if not, refer to parent node)
+
+void tops(Dag&);
+
+struct Dgraph {
+  	using value_type = Val;
+};
+
+
+struct Gnode_ref {};
+struct Gedge_ref {};	// Is an Edge an object? (if not, refer to parent node)
+
+// another Graph representation:
+struct DGN_ref {};
+struct DGE_ref {};	// Is an Edge an object? (if not, refer to parent node)
+
+// use:
+#include <vector>
+using namespace std;
+
+template<Graph G, Vertex_ref R>
+void traverse(G& g, R r)
+{
+	vector<typename G::value_type> found;	// member g::value_type (old habit: could just have used Val)
+  	// ... 
+}
+
+void use1(Tree& t, Dag& d, Dgraph& dg, Node_ref& tr, DAG_vertex_ref& dr, Gnode_ref& gr)
+{
+  traverse(t,tr);
+  traverse(d,dr);
+  traverse(dg,gr);
+}
+
+*/
+
+
+/*
+	Basic idea: provide concepts that define the interface(s) to different kinds of graphs so that you can do
+	basic graph operations and algoriths without knowing exactly which kind of graph it is and keep ignorant
+	about implementation details.
+    
+    Basic design idea: do like the STL
+*/
+/*
+// Graph concepts (like STL containers):
+// Do we need them (STL doesn't make containers explicit)
+template<class G> concept bool Graph =  // general graph operations
+	requires { typename G::value_type; };
+template<class G> concept bool DAG = Graph<G> && requires(G g) { tops(g); };	 // operations simplified for DAGs 
+template<class G> concept bool Tree = DAG<G> && requires(G g) { top(g); };	 // operations simplified for trees
+
+// accessor concepts (like STL Iterators):
+template<class E> concept bool Edge_ref =      // most general and slowest
+	requires(E e) {
+  		typename E::value_type;
+  		{ *e } -> typename E::value_type;
+  		{ e.vertex } -> Vertex_ref;
+	};
+template<class E> concept bool DAG_edge_ref = // operations simplified for DAGs (any extra operations?)
+	Edge_ref<E> && false;	 
+template<class E> concept bool Tree_edge_ref = // operations simplified for trees (any extra operations?)
+	DAG_edge_ref<E> && false; 
+
+template<class V> concept bool Vertex_ref =       // most general and slowest
+  requires(V v, int i) {
+  		typename V::value_type;
+  		{ *v } -> typename V::value_type;
+  		{ v.edge[i] } -> Edge_ref;
+	};
+template<class V> concept bool DAG_vertex_ref = false;  // operations simplified for DAGs (any extra operations?)
+template<class V> concept bool Tree_vertex_ref = false; // operations simplified for DAGs (any extra operations?)
+
+// the value type (in a more general design, this would be a template parmeter):
+struct Val {};
+
+// specific directed graphs (note: we can't assume common structure or common naming from implementation):
+struct Tree {
+  	using value_type = Val;
+};
+
+struct Node_ref {};
+struct Edge_ref {};	// Is an Edge an object? (if not, refer to parent node)
+
+void tops(Tree&);	// return vector Tree_vertex_refs
+Node_ref top(Tree&);
+
+struct Dag {
+  	using value_type = Val;
+};
+
+struct DAG_vertex_ref {};
+struct DAG_edge_ref {};	// Is an Edge an object? (if not, refer to parent node)
+
+void tops(Dag&);
+
+struct Dgraph {
+  	using value_type = Val;
+};
+
+
+struct Gnode_ref {};
+struct Gedge_ref {};	// Is an Edge an object? (if not, refer to parent node)
+
+// another Graph representation:
+struct DGN_ref {};
+struct DGE_ref {};	// Is an Edge an object? (if not, refer to parent node)
+
+// use:
+#include <vector>
+using namespace std;
+
+template<Graph G, Vertex_ref R>
+void traverse(G& g, R r)
+{
+	vector<typename G::value_type> found;	// member g::value_type (old habit: could just have used Val)
+  	// ... 
+}
+
+void use1(Tree& t, Dag& d, Dgraph& dg, Node_ref& tr, DAG_vertex_ref& dr, Gnode_ref& gr)
+{
+  traverse(t,tr);
+  traverse(d,dr);
+  traverse(dg,gr);
+}