Data commit

Task/FizzBuzz/Coq/fizzbuzz.coq

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+Require Import Coq.Lists.List.
+(* https://coq.inria.fr/library/Coq.Lists.List.html *)
+
+Require Import Coq.Strings.String.
+(* https://coq.inria.fr/library/Coq.Strings.String.html *)
+
+Require Import Coq.Strings.Ascii.
+(* https://coq.inria.fr/library/Coq.Strings.Ascii.html *)
+
+Require Import Coq.Init.Nat.
+(* https://coq.inria.fr/library/Coq.Init.Nat.html *)
+
+
+(** Definition of [string_of_nat] to convert natural numbers to strings. *)
+
+Definition ascii_of_digit (n : nat) : ascii :=
+  ascii_of_nat (n + 48).
+
+Definition is_digit (n : nat) : bool :=
+  andb (0 <=? n) (n <=? 9).
+
+Fixpoint rec_string_of_nat (counter : nat) (n : nat) (acc : string) : string :=
+  match counter with
+    | 0 => EmptyString
+    | S c =>
+      if (is_digit n)
+      then String (ascii_of_digit n) acc
+      else rec_string_of_nat c (n / 10) (String (ascii_of_digit (n mod 10)) acc)
+  end.
+(** The counter is only used to ensure termination. *)
+
+Definition string_of_nat (n : nat) : string :=
+  rec_string_of_nat n n EmptyString.
+
+
+(** The FizzBuzz problem. *)
+
+Definition fizz : string :=
+  "Fizz".
+
+Definition buzz : string :=
+  "Buzz".
+
+Definition new_line : string :=
+  String (ascii_of_nat 10) EmptyString.
+
+Definition is_divisible_by (n : nat) (k : nat) : bool :=
+  (n mod k) =? 0.
+
+Definition get_term (n : nat) : string :=
+  if (is_divisible_by n 15) then fizz ++ buzz
+  else if (is_divisible_by n 3) then fizz
+  else if (is_divisible_by n 5) then buzz
+  else (string_of_nat n).
+
+Definition range (a : nat) (b : nat) : list nat :=
+  seq a b.
+
+Definition get_terms (n : nat) : list string :=
+  map get_term (range 1 n).
+
+Definition fizz_buzz : string :=
+  concat new_line (get_terms 100).
+
+(** This shows the string. *)
+Eval compute in fizz_buzz.