109 lines
2.1 KiB
Markdown
109 lines
2.1 KiB
Markdown
## 1.1 - Product
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```Ocaml
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# let rec product = function
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| [] -> 0
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| x::t -> x * product t;;
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```
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## 1.2 - Count
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```Ocaml
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# let rec count x n =
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if x = [] then
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0
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else
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let e::t = x in
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if e = x then
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1 + count t n
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else
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count t n;;
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(* Correction *)
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# let rec count x = function
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| [] -> 0
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| e::t -> (if x = e then 1 else 0) + count x t;;
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val count = 'a -> 'a list -> int = <fun>
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```
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## 1.3 - Search
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```Ocaml
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# let rec search x n =
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if x = [] then
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0
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else
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let e::t = x in
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if e = x then
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true
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else
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search t n;;
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(* Correction *)
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# let search x = function
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| [] -> false
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| e::t -> x = e || search x t
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| _::t -> search x t ;;
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val search 'a -> 'a list -> bool = <fun>
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```
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## 1.4 - $n^{th}$
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```Ocaml
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# let nth l n =
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if n <= 0 then
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invalid_arg "n <= 0"
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else
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let rec nthrec = function
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| ([],_) -> failwith "list too short"
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| (h::_,1)-> h
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| (_::t, n) -> nthrec(t, n-1)
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in
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ntrec(l, n);;
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val nth 'a list -> int -> 'a = <fun>
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```
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## 1.5 - Maximum
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```Ocaml
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# let rec max_value list = match list with
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| [] -> failwith "La liste est vide"
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| [x] -> x
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| hd :: tl ->
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let max_tail = max_value tl in
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if hd > max_tail then hd else max_tail;;
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(* v2 *)
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# let max_value list =
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if list = [] then
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failwith "la list est vide"
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else
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let rec mv = match list with
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| [x] -> x
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| hd :: tl ->
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let max_tail = max_value tl in
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if hd > max_tail then hd else max_tail
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in mv list;;
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```
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## 1.6 - Bonus second
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```Ocaml
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# let rec second_smallest list =
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match list with
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| [] | [_] -> failwith "La liste ne contient pas au moins deux éléments distincts"
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| [x; y] -> if x < y then y else x
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| hd1 :: hd2 :: tl ->
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let min1, min2 =
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if hd1 < hd2 then (hd1, hd2) else (hd2, hd1)
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in
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let rec find_second_smallest rest =
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match rest with
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| [] -> min2
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| hd :: tl ->
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if hd < min1 then find_second_smallest (min1 :: tl)
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else if hd < min2 && hd > min1 then find_second_smallest (hd :: min1 :: tl)
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else find_second_smallest (min2 :: tl)
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in
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find_second_smallest tl;;
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```
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## Exercise 2.1
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```
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let rec arith_list n a r =
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