DLang Front Page Code Example

[Nicholas Londey via Digitalmars-d-learn]

I was looking at this code the other day and thought to my self 
"This is terrible D" in the order of the C hello world with no 
error handling and returning a junk stack value.

I am a reasonably experienced C++ programmer but still a newbie 
at D. However, between the ideals of reusable code and no raw 
loops I felt there must be a better way.

  https://www.youtube.com/watch?v=cQkBOCo8UrE
  http://channel9.msdn.com/Events/GoingNative/2013/Cpp-Seasoning

So I tried rewriting the example on the dlang.org home page and 
came up with the following.

import std.algorithm, std.exception, std.stdio;

double average(T)(T range)
{
   enforce(!range.empty, "No inputs");

   auto totals = range.map!(a => tuple(1.0, 
cast(double)(a))).reduce!((a, b) => tuple(a[0] + b[0], a[1] + 
b[1]));
   return totals[1] / totals[0];
}

void main()
{
   writeln("Average line length: ", stdin.byLine.map!(a => 
a.length).average);
}


In doing so I ran into a few issues.
- Average or mean did not seem to already exist in algorithm or 
numeric.
- I could not think of an easy way to add component wise binaryOp 
to a Tuple.
- Tried using static array instead of tuple but could not work 
out how to crate a static array as the result of a lambda.
- Using dynamic array caused a compile issue and presumably would 
have had terrible heap garbage.

I am not necessarily saying we should replace the existing 
example but was curious what other people thought.