Another update from ingydotnet^djgoku

Task/Fibonacci-sequence/OCaml/fibonacci-sequence-2.ocaml

@@ -3,3 +3,10 @@ let rec fib_rec n =
     n
   else
     fib_rec (n - 1) + fib_rec (n - 2)
+
+(* with support for negatives *)
+let rec fib = function
+    0 -> 0
+  | 1 -> 1
+  | n -> if n > 0 then fib (n-1) + fib (n-2)
+         else fib (n+2) - fib (n+1)

Task/Fibonacci-sequence/OCaml/fibonacci-sequence-3.ocaml

@@ -5,3 +5,8 @@ let fib n =
     | _ -> fib_aux (n-1) b (a+b)
   in
   fib_aux n 0 1
+
+(* support for negatives *)
+let fib n =
+      if n < 0 && n mod 2 = 0 then -fib (abs n)
+      else fib (abs n)

Task/Fibonacci-sequence/OCaml/fibonacci-sequence-4.ocaml

@@ -7,3 +7,13 @@ let fib =
     | n -> fib_aux f1 (f1 +/ f0) (n - 1)
   in
   fib_aux (num_of_int 0) (num_of_int 1)
+
+(* support for negatives *)
+let fib n =
+      if n < 0 && n mod 2 = 0 then minus_num (fib (abs n))
+      else fib (abs n)
+;;
+(* It can be called from the command line with an argument *)
+(* Result is send to standart output *)
+let n = int_of_string Sys.argv.(1) in
+print_endline (string_of_num (fib n))

Task/Fibonacci-sequence/OCaml/fibonacci-sequence-5.ocaml

@@ -1,10 +1,11 @@
 open Num
 
-let mul (a,b,c) (d,e,f) =
-  (a*/d +/ b*/e, a*/e +/ b*/f, b*/e +/ c*/f)
+let mul (a,b,c) (d,e,f) = let bxe = b*/e in
+  (a*/d +/ bxe, a*/e +/ b*/f, bxe +/ c*/f)
 
+let id = (Int 1, Int 0, Int 1)
 let rec pow a n =
-  if n=1 then a else
+  if n=0 then id else
     let b = pow a (n/2) in
     if (n mod 2) = 0 then mul b b else mul a (mul b b)