Problem 3 Write a function buckets : ('a -> 'a > bool) -> 'a list -> 'a list list. that partitions a list into equivalence classes. That is, buckets equiv 1st should return a list of lists where each sublist in the result contains equivalent elements, where two elements are considered equivalent if equiv returns true. For example: buckets () [1;2;3;4] = [[1]; [2]; [3];[4]] buckets () [1; 2; 3; 4; 2; 3; 4;3;4] = [[1]; [2; 2]; [3; 3; 3]; [4; 4;4]] buckets (fun x y-> (=) (x mod 3) (y mod 3)) [1; 2; 3; 4; 5; 6] = [[1;4]; [2;5]; [3;6]] The order of the buckets must reflect the order in which the elements appear in the original list. For example, the output of buckets (=) [1;2;3;4] should be [[1]; [2]; [3]; [4]] and not [[2]; [1]; [3]; [4]] or any other permutation. The order of the elements in each bucket must reflect the order in which the elements appear in the original list. For example, the output of buckets (fun x y (=) (x mod 3) (y mod 3)) [1; 2; 3; 4; 5; 6] should be [[1;4]; [2;5]; [3;6]] and not [[4; 1]; [5;2]; [3;6]] or any other permutations. Assume that the comparison function ('a -> 'a -> bool) is commutative, associative and idempotent. Just use lists. Do not use sets or hash tables. List append function @ may come in handy. [1;2;3] @[4; 5; 6] [1; 2; 3; 4; 5; 6].

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Problem 3
In [ ]:
Write a function
buckets : ('a -> 'a -> bool) -> 'a list -> 'a list list
that partitions a list into equivalence classes. That is, buckets equiv 1st should return a list of lists where each sublist in the result contains equivalent
elements, where two elements are considered equivalent if equiv returns true. For example:
buckets (=) [1; 2; 3; 4] = [[1]; [2] ; [3]; [4]]
buckets (=) [1; 2; 3; 4; 2; 3; 4; 3; 4]
buckets (fun x y -> (=) (x mod 3)
[[1;4]; [2;5]; [3; 6]]
The order of the buckets must reflect the order in which the elements appear in the original list. For example, the output of buckets (=) [1;2;3;4]
should be [[1] ; [2] ; [3] ; [4]] and not [[2]; [¹]; [3]; [4]] or any other permutation.
=
The order of the elements in each bucket must reflect the order in which the elements appear in the original list. For example, the output of buckets (fun x
y -> (=) (x mod 3) (y mod 3)) [1; 2; 3; 4; 5; 6] should be [[1;4]; [2;5]; [3;6]] and not [[4;1]; [5;2]; [3;6]] or any other
permutations.
Just use lists. Do not use sets or hash tables.
[[1]; [2; 2]; [3; 3; 3]; [4; 4;4]]
(y mod 3)) [1; 2; 3; 4; 5; 6]
Assume that the comparison function ('a -> 'a -> bool) is commutative, associative and idempotent.
In [] let buckets p 1 =
List append function @ may come in handy. [1;2;3] @ [4;5;6]
(* YOUR CODE HERE *)
assert (buckets (=) [1; 2; 3; 4] [[¹]; [2] ; [3]; [4]]);
assert (buckets (=) [1; 2; 3; 4; 2; 3; 4; 3; 4]
assert (buckets (fun x y -> (=) (x mod 3)
=
=
[1; 2; 3; 4; 5; 6].
[[1]; [2; 2]; [3; 3; 3]; [4; 4; 4]]);
(y mod 3)) [1; 2; 3; 4; 5; 6]
=
[[1;4]; [2;5]; [3; 6]])
Transcribed Image Text:Problem 3 In [ ]: Write a function buckets : ('a -> 'a -> bool) -> 'a list -> 'a list list that partitions a list into equivalence classes. That is, buckets equiv 1st should return a list of lists where each sublist in the result contains equivalent elements, where two elements are considered equivalent if equiv returns true. For example: buckets (=) [1; 2; 3; 4] = [[1]; [2] ; [3]; [4]] buckets (=) [1; 2; 3; 4; 2; 3; 4; 3; 4] buckets (fun x y -> (=) (x mod 3) [[1;4]; [2;5]; [3; 6]] The order of the buckets must reflect the order in which the elements appear in the original list. For example, the output of buckets (=) [1;2;3;4] should be [[1] ; [2] ; [3] ; [4]] and not [[2]; [¹]; [3]; [4]] or any other permutation. = The order of the elements in each bucket must reflect the order in which the elements appear in the original list. For example, the output of buckets (fun x y -> (=) (x mod 3) (y mod 3)) [1; 2; 3; 4; 5; 6] should be [[1;4]; [2;5]; [3;6]] and not [[4;1]; [5;2]; [3;6]] or any other permutations. Just use lists. Do not use sets or hash tables. [[1]; [2; 2]; [3; 3; 3]; [4; 4;4]] (y mod 3)) [1; 2; 3; 4; 5; 6] Assume that the comparison function ('a -> 'a -> bool) is commutative, associative and idempotent. In [] let buckets p 1 = List append function @ may come in handy. [1;2;3] @ [4;5;6] (* YOUR CODE HERE *) assert (buckets (=) [1; 2; 3; 4] [[¹]; [2] ; [3]; [4]]); assert (buckets (=) [1; 2; 3; 4; 2; 3; 4; 3; 4] assert (buckets (fun x y -> (=) (x mod 3) = = [1; 2; 3; 4; 5; 6]. [[1]; [2; 2]; [3; 3; 3]; [4; 4; 4]]); (y mod 3)) [1; 2; 3; 4; 5; 6] = [[1;4]; [2;5]; [3; 6]])
Expert Solution
Step 1
let buckets (f:'a->'a->bool) (lst:'a list): 'a list list =
 
let rec find (find_f: 'a->'a->bool)(find_ht: 'a) (find_acc:'a list list):'a list list =
 
match find_acc with
 
[]-> [[find_ht]]
 
| head::tail -> match head with h::_-> if f h find_ht then (find_ht::head)::tail else head::(find f find_ht tail)
 
in
 
let rec parse (parse_f: 'a->'a->bool) (parse_lst:'a list) (parse_acc: 'a list list): 'a list list =
 
match parse_lst with
 
[] -> parse_acc
 
| ht::tl -> parse f tl (find f ht parse_acc)
 
in
 
match lst with
 
[]->[]
 
| ht::tl -> parse f tl [[ht]];;
 
buckets ( = ) [1;2;3;4];;
 
buckets ( = ) [1;2;3;4;2;3;4;3;4];;
 
buckets (fun x y -> ( = ) (x mod 3) (y mod 3) ) [1;2;3;4;5;6];;
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