ch-ch-update: series, closed-form series, and strides

[Andrei Alexandrescu]

I've updated my code and documentation to include series (as in math) in 
the form of infinite ranges. Also series in closed form (given n can 
compute the nth value without iterating) are supported as random-access 
ranges.

Also Stride is provided. The Matrix container (speaking of scientific 
computing with D!) will support various representational choices, most 
importantly the ones endorsed by high-performance libraries. For Matrix, 
Stride is an important component as I'm sure anyone who's ever written a 
matrix knows.

http://ssli.ee.washington.edu/~aalexand/d/web/phobos/std_range.html
http://ssli.ee.washington.edu/~aalexand/d/web/phobos/std_algorithm.html

Back to series. Finally my dream has come true: I can define a decent 
Fibonacci series clearly and efficiently in one line of code. No more 
idiotic recursive function that takes exponential time to finish!

auto fib = series!("a[n-1] + a[n]")(1, 1);
// write 10 Fibonacci numbers
foreach (e; take(10, fib)) writeln(e);

This means:

* The state of the series consists of two values, which start as a[0] = 
1 and a[1] = 1. This state will be stored inside the returned object 
in-situ (no dynamic allocation).

* The means to compute the n+1'th element given the n'th and the n-1'th 
is a[n-1] + a[n].

The series object takes care of everything - keeping score, rotating 
buffers, advancing state, you name it.

Walter sent me examples of famous series (e.g. Taylor, approximations of 
pi, etc.) that I want to put in as examples. I can't wait the next 
release so I can share this all with you guys!

Feedback and suggestions welcome! (I know, I need to add the iota range 
presto!)


Andrei