simlun · July 7, 2012 22:22 · Jul 7, 2012 · Jul 7, 2012 · Jul 7, 2012
diff --git a/euler_test.clj b/euler_test.clj
@@ -12,7 +12,7 @@
 
 (fact "fib can handle even bigint-large numbers, just for fun"
   (fib 92) => 7540113804746346429 
-  (fib 93) => 12200160415121876738N) 
+  (fib 93) => 12200160415121876738) 
 
 (fact "The Project Euler problem 2 answer"
   (sum-even-fibs-less-than 4000000) => 4613732)
diff --git a/euler_test.clj b/euler_test.clj
@@ -10,7 +10,7 @@
   (fib 4) => 3
   (fib 12) => 144) 
 
-(fact "fib can handle even bigint-large numbers"
+(fact "fib can handle even bigint-large numbers, just for fun"
   (fib 92) => 7540113804746346429 
   (fib 93) => 12200160415121876738N) 
 

diff --git a/euler.clj b/euler.clj
@@ -0,0 +1,27 @@
+(ns euler002.euler)
+
+(defn- fib-fast 
+  [i a b limit]
+  (if 
+    (< i limit)
+    (fib-fast (inc i) b (+ a b) limit)
+    b))
+
+(defn fib 
+  [n]
+  (if
+    (= n 0)
+    0
+    (fib-fast (bigint 1) (bigint 0) (bigint 1) (bigint n))))
+
+(defn- even-fibs-less-than
+ [max-fib]
+  (for [n (range)
+      :let [f (fib n)]
+      :when (even? f)
+      :while (< f max-fib)]
+  f))
+
+(defn sum-even-fibs-less-than
+  [max-fib]
+  (reduce + (even-fibs-less-than max-fib)))
diff --git a/euler_test.clj b/euler_test.clj
@@ -0,0 +1,18 @@
+(ns euler002.euler-test
+  (:use midje.sweet
+        euler002.euler))
+
+(fact
+  (fib 0) => 0
+  (fib 1) => 1
+  (fib 2) => 1
+  (fib 3) => 2
+  (fib 4) => 3
+  (fib 12) => 144) 
+
+(fact "fib can handle even bigint-large numbers"
+  (fib 92) => 7540113804746346429 
+  (fib 93) => 12200160415121876738N) 
+
+(fact "The Project Euler problem 2 answer"
+  (sum-even-fibs-less-than 4000000) => 4613732)
No results found