lecture 02 + lab 01

lab01/lab1.ml

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+(** [reverse l] returns the reverse order of list [l]; non tail recursive *)
+let rec reverse l =
+  match l with
+  | [] -> []
+  | x :: xs -> reverse xs @ [x];;
+
+(**/**)
+let test_reverse () =
+  assert (reverse [] = []);
+  assert (reverse [1] = [1]);
+  assert (reverse [1; 2] = [2; 1])
+(**/**)
+
+(** [reverse_tr l] returns the reverse order of list [l]; tail recursive *)
+let reverse_tr l =
+  let rec reverse_tr' acc l =
+    match l with
+    | [] -> acc
+    | x :: xs -> reverse_tr' (x :: acc) xs
+  in
+  reverse_tr' [] l;;
+
+(**/**)
+let test_reverse_tr () =
+  assert (reverse_tr [] = []);
+  assert (reverse_tr [1] = [1]);
+  assert (reverse_tr [1; 2] = [2; 1])
+(**/**)
+
+(** [zip l1 l2] combines elements from [l1] and [l2] into a
+  * new list of tuples; non tail recursive
+  *)
+let rec zip l1 l2 =
+  match l1, l2 with
+  | [], _ | _, [] -> [] (* if l1 or l2 is empty, return empty *)
+  | x1 :: xs1, x2 :: xs2 ->
+    (x1, x2) :: zip xs1 xs2;;
+
+(**/**)
+let test_zip () =
+  assert (zip [] [] = []);
+  assert (zip [1] [] = []);
+  assert (zip [] ['a'] = []);
+  assert (zip [1; 2; 3] ['a'; 'b'] = [(1, 'a'); (2, 'b')]);
+  assert (zip [1; 2; 3] ['a'; 'b'; 'c'] = [(1, 'a'); (2, 'b'); (3, 'c')])
+(**/**)
+
+(** [zip_tr l1 l2] combines elements from [l1] and [l2] into a
+  * new list of tuples; tail recursive
+  *)
+let zip_tr l1 l2 =
+  let rec zip_tr' acc l1 l2 =
+    match l1, l2 with
+    | [], _ | _, [] -> reverse_tr acc (* if l1 or l2 is empty, return empty *)
+    | x1 :: xs1, x2 :: xs2 ->
+      zip_tr' ((x1, x2) :: acc) xs1 xs2
+  in
+  zip_tr' [] l1 l2;;
+
+(**/**)
+let test_zip_tr () =
+  assert (zip_tr [] [] = []);
+  assert (zip_tr [1] [] = []);
+  assert (zip_tr [] ['a'] = []);
+  assert (zip_tr [1; 2; 3] ['a'; 'b'] = [(1, 'a'); (2, 'b')]);
+  assert (zip_tr [1; 2; 3] ['a'; 'b'; 'c'] = [(1, 'a'); (2, 'b'); (3, 'c')])
+(**/**)
+
+(** [unzip l] takes in a list of tuples [l] where each tuple is
+  * a pair, we seperate the pairs (x, y) into sepeate lists, ([x], [y])
+  * and return a tuple of both lists; non tail recursive *)
+let rec unzip l =
+  match l with
+  | [] -> ([], [])
+  | (x, y) :: xys ->
+    let (l1, l2) = unzip xys in
+      x :: l1, y :: l2;;
+
+(**/**)
+let test_unzip () =
+  assert (unzip [] = ([], []));
+  assert (unzip [(1, 'a')] = ([1], ['a']));
+  assert (unzip [(1, 'a'); (2, 'b')] = ([1; 2], ['a'; 'b']))
+(**/**)
+
+(** [unzip_tr l] takes in a list of tuples [l] where each tuple is
+  * a pair, we seperate the pairs (x, y) into sepeate lists, ([x], [y])
+  * and return a tuple of both lists; tail recursive *)
+let unzip_tr l =
+  let rec unzip_tr' (a1, a2) l =
+    match l with
+    | [] -> (a1, a2)
+    | (x, y) :: xys ->
+      unzip_tr' (x :: a1, y :: a2) xys
+  in
+  unzip_tr' ([], []) (reverse_tr l);;
+
+(**/**)
+let test_unzip_tr () =
+  assert (unzip_tr [] = ([], []));
+  assert (unzip_tr [(1, 'a')] = ([1], ['a']));
+  assert (unzip_tr [(1, 'a'); (2, 'b')] = ([1; 2], ['a'; 'b']))
+(**/**)
+
+(** [dedup l] takes in a list [l] and collapses consecutive duplicated
+  * elements into a single element; non tail recursive *)
+let rec dedup l =
+  match l with
+  | [] -> []
+  | [x] -> l
+  | x :: y :: zs ->
+    if x = y then dedup (x :: zs)
+    else x :: dedup (y :: zs);;
+
+(**/**)
+let test_dedup () =
+  assert (dedup [] = []);
+  assert (dedup [1] = [1]);
+  assert (dedup [1; 2] = [1; 2]);
+  assert (dedup [1; 1; 2; 2; 2; 1; 3; 3; 2] = [1; 2; 1; 3; 2])
+(**/**)
+
+(** [dedup l] takes in a list [l] and collapses consecutive duplicated
+  * elements into a single element; tail recursive *)
+let dedup_tr l =
+  let rec dedup' acc l =
+    match l with
+    | [] -> acc
+    | [x] -> l
+    | x :: y :: zs ->
+      if x = y then dedup' (x :: acc) (x :: zs)
+      else x :: dedup' (x :: acc) (y :: zs)
+  in
+  dedup' [] l;;
+
+(**/**)
+let test_dedup_tr () =
+  assert (dedup_tr [] = []);
+  assert (dedup_tr [1] = [1]);
+  assert (dedup_tr [1; 2] = [1; 2]);
+  assert (dedup_tr [1; 1; 2; 2; 2; 1; 3; 3; 2] = [1; 2; 1; 3; 2])
+(**/**)
+
+(**/**)
+let run_all_tests () =
+  test_reverse();
+  test_reverse_tr();
+  test_zip();
+  test_zip_tr();
+  test_unzip();
+  test_unzip_tr();
+  test_dedup();
+  test_dedup_tr();
+(**/**)