Better explanation of the unless procesure if it is not defined

[sicp.git] / src / sicp / ch2_1_extended.clj

diff --git a/src/sicp/ch2_1_extended.clj b/src/sicp/ch2_1_extended.clj
index 399b66246a0ef72112ed38b2fc1b7811e6a0ae3e..0631e7dfb9201a1b1faa7af83fdcc01bc11c28fd 100644 (file)
--- a/src/sicp/ch2_1_extended.clj
+++ b/src/sicp/ch2_1_extended.clj
@@ -32,3 +32,14 @@
 
 (defn width [i]
   (/ (- (upper-bound i) (lower-bound i)) 2))
+
+;; parallel-resistor formula
+(defn par1 [r1 r2]
+  (div-interval (mul-interval r1 r2)
+               (add-interval r1 r2)))
+
+(defn par2 [r1 r2]
+  (let [one (make-interval 1 1)]
+    (div-interval one
+                 (add-interval (div-interval one r1)
+                               (div-interval one r2)))))