refactor: day 1 part 1

src/day01.rkt

@@ -41,15 +41,18 @@
 
 
 ; From a char list returns the first digit it finds as a char, or nil
+; char list -> char
 (define (get-first-digit list)
-  (if (= (length list) 0)
-      null
-      (let ([current-char (first list)])
-        (if (char-numeric? current-char)
+    (if (empty? list)
+        null
+        (let ([current-char (first list)])
+          (if (char-numeric? current-char)
             current-char
             (get-first-digit (rest list))))))
 
-; ??
+
+; finds the last digit in the given list
+; char list -> char
 (define (get-last-digit list carry)
   (if (= (length list) 0)
       carry
@@ -61,6 +64,7 @@
         (get-last-digit (rest list) next-char))))
 
 ; Creates a new number from the first & last number found inside a char list
+; char list -> int
 (define (list->digits list)
     (let ([first-char (get-first-digit list)]
           [last-char (get-last-digit list -1)])
@@ -80,3 +84,7 @@
     (define sum (foldl + 0 list-of-digits))
 
     (number->string sum))
+
+(define (advent-of-code-01-p2)
+  0)
+