initial commit a6.scm

a6.scm

@@ -0,0 +1,56 @@
+"problem 1. (a)"
+(define (count-positives lst)
+  (define (iter l count)
+    (cond ((= (length l) 0) count)
+          ((> (car l) 0) (iter (cdr l) (+ count 1)))
+          (else (iter (cdr l) count))))
+  (iter lst 0))
+
+"problem 1. (b)"
+(define (multiply-list lst)
+  (define (iter acc l)
+    (if (= (length l) 0)
+        acc
+        (iter (* acc (car l)) (cdr l))))
+  (iter 1 lst))
+
+"problem 1. (c)"
+(define (consecutive-ints a b)
+  (define (iter l i)
+    (if (< i a)
+        l
+        (iter (cons i l) (- i 1))))
+  (iter (list) b))
+
+"problem 1. (d)"
+(define (consecutive-squares a b)
+  (define (iter l i)
+    (if (< i a)
+        l
+        (iter (cons (* i i) l) (- i 1))))
+  (iter (list) b))
+
+"problem 2."
+(define (count-if f lst)
+  (define (iter l count)
+    (cond ((= (length l) 0) count)
+          ((f (car l)) (iter (cdr l) (+ count 1)))
+          (else (iter (cdr l) count))))
+  (iter lst 0))
+
+"problem 3. (a)"
+(define (nth-filtered f n)
+  (define (iter i count)
+    (if (f i)
+        (if (= count n)
+            i
+            (iter (+ i 1) (+ count 1)))
+        (iter (+ i 1) count )))
+  (iter 1 1))
+
+"problem 3. (b)"
+(define (min-value f a b)
+  (if (< (abs (- b a)) 0.0001)
+      (f a)
+      (let ((m (/ (+ a b) 2)))
+        (min (min-value f a m) (min-value f m b)))))