Add 1.2, 1.3 and 1.7 exs

sicp-ex-1.2.rkt

@@ -0,0 +1,7 @@
+(define the-numerator
+  (+ 5 4 (- 2 (- 3 (+ 6 (/ 4 5))))))
+
+(define the-denominator
+  (* 3 (- 6 2)(- 2 7)))
+
+(/ the-numerator the-denominator)

sicp-ex-1.3.rkt

@@ -0,0 +1,11 @@
+(define (square x) (* x x))
+(define (sum-of-squares x y) (+ (square x) (square y)))
+(define (is-first-least? a b c) (and (< a b) (< a c)))
+
+(define a 9)
+(define b 1)
+(define c 10)
+
+(cond ((is-first-least? c a b)(sum-of-squares a b))
+      ((is-first-least? a c b)(sum-of-squares c b))
+      ((is-first-least? b a c)(sum-of-squares a c)))

sicp-ex-1.7.rkt

@@ -0,0 +1,23 @@
+(define (sqrt-iter guess guess-prev x) 
+  (if (good-enough? guess guess-prev) 
+      guess 
+      (sqrt-iter (improve guess x) guess 
+                 x))) 
+
+(define (improve guess x)
+  (average guess (/ x guess)))
+
+(define (average x y)
+  (/ (+ x y) 2))
+
+(define (good-enough? guess guess-prev) 
+  (< (abs (- guess guess-prev)) 0.001)) 
+
+(define (sqrt-new x)
+  (if (= x 0) x (sqrt-iter 1.0 999 x)))
+
+(sqrt-new 16)
+(sqrt-new 1.0004)
+(sqrt-new 1)
+(sqrt-new 134895724398)
+(sqrt-new 0)