Added an example application that displays statistics about YAML

documents.

examples/yaml_stats/Makefile

@@ -0,0 +1,5 @@
+main:
+	dmd -w -I../../ -L-L../../ -L-ldyaml yaml_stats.d
+
+clean:
+	rm yaml_stats myaml_stats.o

examples/yaml_stats/small.yaml

@@ -0,0 +1,4 @@
+- 1
+- 2 : 'a'
+  3 : 'b'
+- 4 : [1.0, 2.1, 3.2]

examples/yaml_stats/yaml_stats.d

@@ -0,0 +1,104 @@
+
+///Example D:YAML application that displays statistics about YAML documents.
+
+import std.stdio;
+import std.string;
+import yaml;
+
+
+///Collects statistics about a YAML document and returns them as string.
+string statistics(ref Node document)
+{
+    size_t nodes;
+    size_t scalars, sequences, mappings;
+    size_t seqItems, mapPairs;
+
+    size_t[string] tags;
+
+    void crawl(ref Node root)
+    {
+        ++nodes;
+        if((root.tag in tags) is null)
+        {
+            tags[root.tag] = 0;
+        }
+        ++tags[root.tag];
+
+        if(root.isScalar)
+        {
+            ++scalars;
+            return;
+        }
+        if(root.isSequence)
+        {
+            ++sequences;
+            seqItems += root.length;
+            foreach(ref Node node; root)
+            {
+                crawl(node);
+            }
+            return;
+        }
+        if(root.isMapping)
+        {
+            ++mappings;
+            mapPairs += root.length;
+            foreach(ref Node key, ref Node value; root)
+            {
+                crawl(key);
+                crawl(value);
+            }
+            return;
+        }
+    }
+
+    crawl(document);
+
+    string tagStats = "\nTag statistics:\n";
+    foreach(tag, count; tags)
+    {
+        tagStats ~= format("\n", tag, " : ", count);
+    }
+
+    return format(  "\nNodes:                   ", nodes, 
+                  "\n\nScalars:                 ", scalars,
+                    "\nSequences:               ", sequences,
+                    "\nMappings:                ", mappings,
+                  "\n\nAverage sequence length: ", cast(real)seqItems / sequences,
+                    "\nAverage mapping length:  ", cast(real)mapPairs / mappings,
+                  "\n\n", tagStats);
+}
+
+void main(string[] args)
+{
+    //Help message
+    if(args.length == 1)
+    {
+        writeln("Usage: yaml_stats [YAML_FILE ...]\n");
+        writeln("Analyzes YAML files with provided filenames and displays statistics.");
+        return;
+    }
+
+    //Print stats about every document in every file.
+    foreach(file; args[1 .. $])
+    {
+        writeln("\nFile ", file);
+        writeln("------------------------------------------------------------");
+        try
+        {
+            auto loader = Loader(file);
+
+            size_t idx = 0;
+            foreach(ref document; loader)
+            {
+                writeln("\nDocument ", idx++);
+                writeln("----------------------------------------");
+                writeln(statistics(document));
+            }
+        }
+        catch(YAMLException e)
+        {
+            writeln("ERROR: ", e.msg);
+        }
+    }
+}