Day 1 part 1 sample

main.rkt

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+#lang racket
+
+; You try to ask why they can't just use a weather machine ("not powerful enough")
+; and where they're even sending you ("the sky") and why your map looks mostly
+; blank ("you sure ask a lot of questions") and hang on did you just say the sky
+; ("of course, where do you think snow comes from") when you realize that the
+; Elves are already loading you into a trebuchet ("please hold still, we need
+; to strap you in").
+
+; As they're making the final adjustments, they discover that their calibration
+; document (your puzzle input) has been amended by a very young Elf who was
+; apparently just excited to show off her art skills. Consequently, the Elves
+; are having trouble reading the values on the document.
+
+; The newly-improved calibration document consists of lines of text; each line
+; originally contained a specific calibration value that the Elves now need to
+; recover. On each line, the calibration value can be found by combining the
+; first digit and the last digit (in that order) to form a single two-digit
+; number.
+
+; For example:
+
+; 1abc2
+; pqr3stu8vwx
+; a1b2c3d4e5f
+; treb7uchet
+
+; In this example, the calibration values of these four lines are 12, 38, 15,
+; and 77. Adding these together produces 142.
+
+; Consider your entire calibration document. What is the sum of all of the
+; calibration values?
+
+(define input '("1abc2"
+                "pqr3stu8vwx"
+                "a1b2c3d4e5f"
+                "treb7uchet"))
+
+; From a char list returns the first digit it finds as a char, or nil
+(define (get-first-digit list)
+  (if (= (length list) 0)
+      null
+      (let ([current-char (first list)])
+        (if (char-numeric? current-char)
+            current-char
+            (get-first-digit (rest list))))))
+
+(define (get-last-digit list carry)
+  (if (= (length list) 0)
+      carry
+      (let* ([current-char (first list)]
+             [next-char
+              (if (char-numeric? current-char)
+                  current-char
+                  carry)])
+        (get-last-digit (rest list) next-char))))
+
+; Creates a new number from the first & last number found inside a string
+(define (list->digits list)
+    (let ([first-char (get-first-digit list)]
+          [last-char (get-last-digit list -1)])
+      (string->number (string first-char last-char))))
+
+
+(define char-list (map string->list input))
+(define result (foldl + 0 (map list->digits char-list)))
+
+(print result)
+
+
+
+