Add licensing information (#12)

Also an .gitignore

.gitignore

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+/target

COPYING

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+This project is dual-licensed under the Apache 2.0 and MIT licenses.
+
+You may use this code under the terms of either license.

LICENSE_APACHE.md

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+   Copyright 2021 Daniel Vainsencher and Daniel Fox
+
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LICENSE_MIT.md

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+MIT License
+
+Copyright (c) 2021 Daniel Vainsencher and Daniel Fox
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
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+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

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-# You have a numerical problem. 
+Iterative methods and associated utilities in Rust.
 
-## You applied an iterative method naively, now you have 10 problems that recur forever.
-
-Suppose we have a problem, and initial solution (probably bad) and a
-function f such that f(x) is a better solution than x by some numeric
-cost measure g. Then applying f repeatedly gives us a sequence of ever
-better solutions, hopefully converging to an optimal solution. The
-most common initial "I want to see this work!" implementation looks
-like:
-
-	x = x0
-	for i in 100:
-		x = f(x)
-
-But as soon as you've implemented such a method, many additional
-considerations come up:
-- are 100 iterations enough? 
-- are x actually ever improving? 
-- how long is each iteration taking? 
-- perhaps we want to log every 10th x for later plotting?
-- it crashed after 2 days of iterations, perhaps I should have saved
-  intermediate iterations...
-
-Following the path of least resistance, we might add `print(g(x))` at
-the end, move `print(g(x))` into the loop, use timers and print
-differences, etc. In general, we find ourselves adding a few lines of
-code, then moving, deleting, re-adding, commenting them out... and on
-the next project perhaps copy and pasting them again. 
-
-Some of the time, answering our questions require access to internal
-state of f, which therefore gets inlined into the loop, and now all
-these external concerns are mixed with the algorithm, possibly adding
-bugs to the very algorithm they were supposed to help understand!
-
-Argh! 
-
-## Can't we just write the algorithm once, write each utility once, and somehow do only the wiring together we need? 
-
-Yes, kind of, but it is language specific. LT;DR:
-
-* f should not be a black box that transforms solutions x; it should
-  instead take and returns a struct s with all interesting state of
-  the algorithm.
-* To start the sequence of states, convert a problem p into an initial
-  state s0
-* Abstract the repeated application of f as a stream of states s,
-  assuming your language has one.
-* Abstract the utilities as stream adaptors. Such a utility takes a
-  stream and applies to each a transformation (e.g., measure value), a
-  side effect (log some states) or both.
-
-I did not invent this approach, and will happily add further
-references!; briefly, this hope has a long history of programming
-language specific ([a Haskell mailing list circa
-2006](https://mail.haskell.org/pipermail/haskell-cafe/2006-August/017394.html))
-answers. A recent and nice entry tackling this problem in Julia is
-"[Iterative methods done right (because life is too short to write
-for-loops)](http://lostella.github.io/2018/07/25/iterative-methods-done-right.html)"
-(referred to as IM below) proposes to write iterative methods as Julia
-iterators and various utilities for them as iterator adaptors. I
-recommend reading their exposition, which inspired this project!
-
-# How deep can we follow this path in rust?
-
-Rust seems promising for many reasons. 
-
-* Rust loves abstracting sequences; iterators are a (the?) first class
-  citizen in, e.g., for loops.
-* In Rust abstraction costs are low, so won't dominate the work even
-  when iterations are pretty cheap.
-* It is a language essentially optimized for writing high efficiency
-  reusable abstractions, so when iterator is not an exact fit, we can
-  use a variation.
-
-## The simplest thing and how it fails
-
-In simple cases, Rust iterators will do. We even have some nice little
-adaptors pre-made, like `enumerate` with annotates our state with its
-location in the stream, and `take` which stops after the given
-iteration number:
-
-    for (i, state) in convert_problem_to_iterator(problem).enumerate().take(4) {
-        println!("Iteration {} has state {}", i, state);
-    }
-
-
-# TODO here
-* rework the fib example, can we actually output the state instead of
-  the next value?
-* Understand rustdoc better. Link to the fib code examples? Does it
-  make sense to make this whole essay literate code using rustdoc?
-
-And we can go quite far with this direction, as long as state is cheap
-to copy. The caveat is because iterators return values, not
-references, and so for the iterator to own them and the loop body and
-down stream adaptors to have access requires copies. Some might be
-optimized away by a [sufficiently smart
-compiler](https://wiki.c2.com/?SufficientlySmartCompiler) and Rust is
-plenty smart, but the Rusty approach to reliable efficiency is to
-minimize copies and make them explicit.
-
-Some unprocessed links:
-
-1. https://docs.rs/streaming-iterator/0.1.5/streaming_iterator/
+# Licensing
 
+This project is dual-licensed under the [Apache](LICENSE_APACHE.md)
+and [MIT](LICENSE_MIT.md) licenses. You may use this code under the
+terms of either license. Contributing to this repo in any form
+constitutes agreement to license any such contributions under all
+licenses specified in the COPYING file at that time.