update

Task/Four-bit-adder/Haskell/four-bit-adder-1.hs

@@ -1,4 +1,5 @@
 import Control.Arrow
+import Data.List (mapAccumR)
 
 bor, band :: Int -> Int -> Int
 bor = max

Task/Four-bit-adder/Haskell/four-bit-adder-3.hs

@@ -1,4 +1,4 @@
 halfAdder = uncurry band &&& uncurry xor
 fullAdder (c, a, b) =  (\(cy,s) ->  first (bor cy) $ halfAdder (b, s)) $ halfAdder (c, a)
 
-adder4 as = foldr (\(f,a,b) (cy,bs) -> second(:bs) $ f (cy,a,b)) (0,[]). zip3 (replicate 4 fullAdder) as
+adder4 as = mapAccumR (\cy (f,a,b) -> f (cy,a,b)) 0 . zip3 (replicate 4 fullAdder) as

Task/Four-bit-adder/Racket/four-bit-adder.rkt

@@ -0,0 +1,46 @@
+#lang racket
+
+(define (adder-and a b)
+  (if (= 2 (+ a b)) 1 0))    ; Defining the basic and function
+
+(define (adder-not a)
+  (if (zero? a) 1 0))        ; Defining the basic not function
+
+(define (adder-or a b)
+  (if (> (+ a b) 0) 1 0))    ; Defining the basic or function
+
+(define (adder-xor a b)
+  (adder-or
+   (adder-and
+    (adder-not a)
+    b)
+   (adder-and
+    a
+    (adder-not b))))         ; Defines the xor function based on the basic functions
+
+(define (half-adder a b)
+  (list (adder-xor a b) (adder-and a b))) ; Creates the half adder, returning '(sum carry)
+
+(define (adder a b c0)
+  (define half-a (half-adder c0 a))
+  (define half-b (half-adder (car half-a) b))
+  (list
+   (car half-b)
+   (adder-or (cadr half-a) (cadr half-b))))  ; Creates the full adder, returns '(sum carry)
+
+(define (n-bit-adder 4a 4b)   ; Creates the n-bit adder, it receives 2 lists of same length
+  (let-values                 ; Lists of the form '([01]+)
+      (((4s v)                ; for/fold form will return 2 values, receiving this here
+        (for/fold ((S null) (c 0)) ;initializes the full sum and carry
+          ((a (in-list (reverse 4a))) (b (in-list (reverse 4b))))
+          ;here it prepares variables for summing each element, starting from the least important bits
+          (define added
+            (adder a b c))
+          (values
+           (cons (car added) S) ; changes S and c to it's new values in the next iteration
+           (cadr added)))))
+    (if (zero? v)
+        4s
+        (cons v 4s))))
+
+(n-bit-adder '(1 0 1 0) '(0 1 1 1)) ;-> '(1 0 0 0 1)