Demonstrate nested ifs (bis)

outline/flow_control.md

@@ -177,7 +177,16 @@ ng-click="block21=!block21"></button>
 {: ng-show="block62" .description}
 
 ```clojure
-(cond
+(if (> (+ y 40) 150)        ; if over the top
+    -150                    ;   then start at the bottom
+    (if (< (+ y 40) -150)   ;   if below the bottom
+        150                 ;     then start at the top
+        (+ y 40)))          ;     otherwise move
+
+```
+
+```clojure
+(cond                       ; so much more legible than nested ifs
   (> (+ y 40) 150) -150
   (< (+ y 40) -150) 150
   :else (+ y 40)))
@@ -192,10 +201,24 @@ ng-click="block21=!block21"></button>
   predicate1 expression-to-evaluate-when-predicate1-is-true
   predicate2 expression-to-evaluate-when-predicate2-is-true
   ...
-  :else expression-to-evaluate-when-all-above-are-false)
+  :else      expression-to-evaluate-when-all-above-are-false)
 ```
 </section>
 
+<section ng-controller="NarrativeController">
+#### `cond` example
+
+```clojure
+(cond
+  (< x 10)    "x is smaller than 10"
+  (< 10 x 20) "x is between 10 and 20"
+  (< 20 x 30) "x is between 20 and 30"
+  (< 30 x 40) "x is between 30 and 40"
+  :else       "x is bigger than 40")
+```
+
+</section>
+
 <section>
 #### EXERCISE 2: Y value within a frame - part 2
 {: .slide_title .slide}