Make average line length example more concise

Author: PetarKirov

index.dd

@@ -243,20 +243,17 @@ Modern convenience.
 Modeling power.
 Native efficiency.)
 ----
-#!/usr/bin/env rdmd
-import std.range, std.stdio;
-
 // Compute average line length for stdin
 void main()
 {
-    ulong lines = 0, sumLength = 0;
-    foreach (line; stdin.byLine())
-    {
-        ++lines;
-        sumLength += line.length;
-    }
+    import std.range, std.stdio;
+
+    auto sum = 0.0;
+    auto count = stdin.byLine
+        .tee!(l => sum += l.length).walkLength;
+
     writeln("Average line length: ",
-        lines ? cast(double) sumLength / lines : 0.0);
+        count ? sum / count : 0);
 }
 ----
 ))