fixes #986

xml/chapter4/section1/subsection6.xml

@@ -387,6 +387,45 @@ function f(x) {
  </SNIPPET>
  </LI>
 </OL>
+<SOLUTION>
+ Part (a)
+ <SNIPPET>
+ <JAVASCRIPT>
+// solution provided by GitHub user LucasGdosR
+
+// The Fibonacci function receives n as an argument
+// It applies the fib function recursively, passing n as an argument,
+// as well as the initial arguments (k = 1, fib1 = 1, fib2 = 1)
+(n => (fib => fib(fib, n, 2, 1, 1))
+ // The fib function is then defined as ft,
+ // with parameters n, k, fib1, and fib2
+ // Establish the base cases: n === 1 or n === 2
+ ((ft, n, k, fib1, fib2) => n === 1
+ ? 1
+ : n === 2
+ ? 1
+ :
+ // Iterate until k equals n. Notice k starts at 2, and gets incremented every iteration
+ k === n
+ // When k reaches n, return the accumulated fib2
+ ? fib2
+ // Otherwise, accumulate the sum as the new fib2
+ : ft(ft, n, k + 1, fib2, fib1 + fib2)));
+ </JAVASCRIPT>
+ </SNIPPET>
+ Part (b)
+ <SNIPPET>
+ <JAVASCRIPT>
+// solution provided by GitHub user LucasGdosR
+
+function f(x) {
+ return ((is_even, is_odd) => is_even(is_even, is_odd, x))
+ ((is_ev, is_od, n) => n === 0 ? true : is_od(is_ev, is_od, n - 1),
+ (is_ev, is_od, n) => n === 0 ? false : is_ev(is_ev, is_od, n - 1));
+}
+ </JAVASCRIPT>
+ </SNIPPET>
+</SOLUTION>
  </EXERCISE>
  </JAVASCRIPT>
  </SPLIT>