chore(curriculum): Remove files in wrong format

curriculum/challenges/english/08-coding-interview-prep/rosetta-code/y-combinator.english.md

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+---
+title: Y combinator
+id: 594810f028c0303b75339ad5
+challengeType: 5
+---
+
+## Description
+<section id='description'>
+<p>
+In strict 
+<a href="https://en.wikipedia.org/wiki/Functional programming" title="wp: functional programming">functional programming</a> and
+the <a href="https://en.wikipedia.org/wiki/lambda calculus" title="wp: lambda calculus">lambda calculus</a>, 
+functions (lambda expressions) don't have state and are only allowed to refer to arguments of enclosing functions. 
+This rules out the usual definition of a recursive function wherein a function is associated with the state of a variable and this variable's state is used in the body of the function.
+</p>
+<p>
+The <a href="http://mvanier.livejournal.com/2897.html">Y combinator</a> is itself a stateless function that,
+when applied to another stateless function, returns a recursive version of the function. The Y combinator is
+the simplest of the class of such functions, called 
+<a href="https://en.wikipedia.org/wiki/Fixed-point combinator" title="wp: fixed-point combinator">fixed-point combinators</a>.
+</p>
+Task:
+
+    Define the stateless Y combinator function and use it to compute
+    <a href="https://en.wikipedia.org/wiki/Factorial" title="wp: factorial">factorial</a>.
+
+<code>factorial(N)</code> function is already given to you.
+See also <a href="http://vimeo.com/45140590">Jim Weirich: Adventures in Functional Programming</a>.
+</section>
+
+## Instructions
+<section id='instructions'>
+
+</section>
+
+## Tests
+<section id='tests'>
+
+```yml
+tests:
+  - text: Y must return a function
+    testString: 'assert.equal(typeof Y(f => n => n), ''function'', ''Y must return a function'');'
+  - text: factorial(1) must return 1.
+    testString: 'assert.equal(factorial(1), 1, ''factorial(1) must return 1.'');'
+  - text: factorial(2) must return 2.
+    testString: 'assert.equal(factorial(2), 2, ''factorial(2) must return 2.'');'
+  - text: factorial(3) must return 6.
+    testString: 'assert.equal(factorial(3), 6, ''factorial(3) must return 6.'');'
+  - text: factorial(4) must return 24.
+    testString: 'assert.equal(factorial(4), 24, ''factorial(4) must return 24.'');'
+  - text: factorial(10) must return 3628800.
+    testString: 'assert.equal(factorial(10), 3628800, ''factorial(10) must return 3628800.'');'
+
+```
+
+</section>
+
+## Challenge Seed
+<section id='challengeSeed'>
+
+<div id='js-seed'>
+
+```js
+function Y(f) {
+  return function() {
+  // Good luck!
+  };
+}
+
+var factorial = Y(function(f) {
+  return function (n) {
+    return n > 1 ? n * f(n - 1) : 1;
+  };
+});
+```
+
+</div>
+
+
+### After Test
+<div id='js-teardown'>
+
+```js
+console.info('after the test');
+```
+
+</div>
+
+</section>
+
+## Solution
+<section id='solution'>
+
+
+```js
+var Y = f => (x => x(x))(y => f(x => y(y)(x)));
+
+```
+
+</section>