vault backup: 2023-10-02 14:45:43

Algo/Courses/Chapter 6 - Lists (Exercises).md

@@ -11,9 +11,43 @@ let rec count x n =
 	if x = [] then
 		0
 	else
-		let e::t = x
+		let e::t = x in
 		if e = x then
 			1 + count t n
 		else
-			count t n
+			count t n;;
+```
+
+## 1.3 - Search
+```
+let rec search x n =
+	if x = [] then
+		0
+	else
+		let e::t = x in
+		if e = x then
+			true
+		else
+			search t n;;
+```
+
+## 1.4 - $n^{th}$
+```
+let rec length l = 
+	if l = [] then
+		0
+	else
+		let e::t = l in
+			1 + length t;;
+let rec nth x n =
+	if (x = [] || n =< 0) then
+		Invalid_arg "The number of element in the list is 0"
+	else if length x < n then
+		Failwith "The list is too short"
+	else
+		let e::t = x in
+		if e = x then
+			1 + count t n
+		else
+			count t n;;
 ```