tasks a-s

Task/Repeat-a-string/Mercury/repeat-a-string.mercury

@@ -0,0 +1,26 @@
+:- module repeat.
+:- interface.
+:- import_module string, char, int.
+
+:- func repeat_char(char, int) = string.
+:- func repeat(string, int) = string.
+
+:- implementation.
+:- import_module stream, stream.string_writer, string.builder.
+
+repeat_char(C, N) = string.duplicate_char(C, N).
+
+repeat(String, Count) = Repeated :-
+        S0 = string.builder.init,
+        Repeated = string.builder.to_string(S),
+        printn(string.builder.handle, Count, String, S0, S).
+
+:- pred printn(Stream, int, string, State, State)
+               <= (stream.writer(Stream, string, State),
+                   stream.writer(Stream, character, State)).
+:- mode printn(in, in, in, di, uo) is det.
+printn(Stream, N, String, !S) :-
+        ( N > 0 ->
+                print(Stream, String, !S),
+                printn(Stream, N - 1, String, !S)
+        ; true ).