ch3.ml

(* Questions *)
(* 1. Rewrite the not function from the previous chapter in pattern matching style. *)

let not x =
  match x with
  | x -> false;;

(* 2. Use pattern matching to write a recursive function which, given a positive integer n, returns the *)
(* sum of all the integers from 1 to n. *)

let rec sum n =
  match n with
  | 0 -> 0
  | n -> n + sum (n - 1);;

(* 3. Use pattern matching to write a function which, given two numbers x and n, computes x n. *)

let rec power x n =
  match n with
  | 0 -> 1
  | 1 -> x
  | _ -> x * power x (n -1);;

(* 4. For each of the previous three questions, comment on whether you think it is easier
to read the function with or without pattern matching. How might you expect this to change
if the functions were much larger? *)

(* 5. What does match 1 + 1 with 2 -> match 2 + 2 with 3 -> 4 | 4 -> 5 evaluate to? *)
- : int = 5

(* 6. There is a special pattern x..y to denote continuous ranges of characters,
for example 'a'..'z' will match all lowercase letters. Write functions islower
and isupper, each of type char → bool, to decide on the case of a given letter. *)

let islower c =
  match c with
  | 'a'..'z' -> true
  | _ -> false;;

let isupper c =
  match c with
  | 'A'..'Z' -> true
  | _ -> false;;