RosettaCodeData/Task/Mutual-recursion/Oberon/mutual-recursion.oberon

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MODULE MutualRecursion;
IMPORT Out;
TYPE
Fn = PROCEDURE(n:INTEGER):INTEGER;
PROCEDURE^ M(n:INTEGER):INTEGER;
PROCEDURE F(n:INTEGER):INTEGER;
BEGIN
IF n=0 THEN RETURN 1
ELSE RETURN n-M(F(n-1))
END;
END F;
PROCEDURE M(n:INTEGER):INTEGER;
BEGIN
IF n=0 THEN RETURN 0
ELSE RETURN n-F(M(n-1))
END;
END M;
(* Print the first few values of one of the functions *)
PROCEDURE Show(name:ARRAY OF CHAR;fn:Fn);
CONST Max = 15;
VAR i:INTEGER;
BEGIN
Out.String(name);
Out.String(": ");
FOR i := 0 TO Max DO
Out.Int(fn(i),0);
Out.String(" ");
END;
Out.Ln;
END Show;
(* Show the first values of both F and M *)
BEGIN
Show("F", F);
Show("M", M);
END MutualRecursion.