lecture 02 + lab 01

lab01/expo.ml

@@ -0,0 +1,114 @@
+(** [fact n] calculates the factorial of [n]; non tail recursive *)
+let rec fact n =
+  if n = 0. then 1.
+  else n *. fact(n -. 1.);;
+
+(**/**)
+let test_fact () =
+  assert (fact 0. = 1.);
+  assert (fact 3. = 6.);
+  assert (fact 5. = 120.)
+(**/**)
+
+(** [fact_tr n] calculates the factorial of [n]; tail recursive *)
+let fact_tr n =
+  let rec fact_tr' acc i =
+    if i = 0. then acc
+    else fact_tr' (i *. acc) (i -. 1.)
+  in
+  fact_tr' 1. n;;
+
+(**/**)
+let test_fact_tr () =
+  assert (fact_tr 0. = 1.);
+  assert (fact_tr 3. = 6.);
+  assert (fact_tr 5. = 120.)
+(**/**)
+
+(** [pow_tr a b] calculates [a] to the power of [b]; non tail recursive *)
+let rec pow a b =
+  if b = 0. then 1.
+  else a *. pow a (b -. 1.);;
+
+(**/**)
+let test_pow () =
+  assert (pow 0. 1. = 0.);
+  assert (pow 0. 5. = 0.);
+  assert (pow 1. 0. = 1.);
+  assert (pow 5. 0. = 1.);
+  assert (pow 1. 1. = 1.);
+  assert (pow 5. 1. = 5.);
+  assert (pow 2. 3. = 8.)
+(**/**)
+
+(** [pow_tr a b] calculates [a] to the power of [b]; tail recursive *)
+let pow_tr a b =
+  let rec pow_tr' acc i =
+    if i = 0. then acc
+    else pow_tr' (acc *. a) (i -. 1.)
+  in
+  pow_tr' 1. b;;
+
+(**/**)
+let test_pow_tr () =
+  assert (pow_tr 0. 1. = 0.);
+  assert (pow_tr 0. 5. = 0.);
+  assert (pow_tr 1. 0. = 1.);
+  assert (pow_tr 5. 0. = 1.);
+  assert (pow_tr 1. 1. = 1.);
+  assert (pow_tr 5. 1. = 5.);
+  assert (pow_tr 2. 3. = 8.)
+(**/**)
+
+(** [expo_tr n x] calculates the approximation of e to the power of [x];
+  * with a max iteration detail of [n]; non tail recursive
+  * Require: [n] >= 1
+  *)
+let rec expo n x =
+  if n = 0 then 1.
+  else pow x (float_of_int n) /. fact (float_of_int n) +.
+    expo (n - 1) x;;
+
+(**/**)
+let test_expo () =
+  let tolerance = 1e-6 in
+  let diff = abs_float (expo 20 1. -. exp 1.) in
+  assert (diff < tolerance);
+  let diff = abs_float (expo 20 2. -. exp 2.) in
+  assert (diff < tolerance);
+  let diff = abs_float (expo 20 3. -. exp 3.) in
+  assert (diff < tolerance)
+(**/**)
+
+(** [expo_tr n x] calculates the approximation of e to the power of [x];
+  * with a max iteration detail of [n]; tail recursive
+  * Require: [n] >= 1
+  *)
+let expo_tr n x =
+  let rec expo_tr' acc i =
+    if i = 0 then acc
+    else expo_tr' (acc +. pow_tr x (float_of_int i) /.
+      fact_tr (float_of_int i)) (i - 1)
+  in
+  expo_tr' 1. n;;
+
+(**/**)
+let test_expo_tr () =
+  let tolerance = 1e-6 in
+  let diff = abs_float (expo_tr 20 1. -. exp 1.) in
+  assert (diff < tolerance);
+  let diff = abs_float (expo_tr 20 2. -. exp 2.) in
+  assert (diff < tolerance);
+  let diff = abs_float (expo_tr 20 3. -. exp 3.) in
+  assert (diff < tolerance)
+(**/**)
+
+(**/**)
+let run_all_tests () =
+  test_fact();
+  test_fact_tr();
+  test_pow();
+  test_pow_tr();
+  test_expo();
+  test_expo_tr()
+(**/**)