Initial data commit

Task/Totient-function/ALGOL-M/totient-function.alg

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+BEGIN
+
+%  RETURN P MOD Q  %
+INTEGER FUNCTION MOD (P, Q);
+INTEGER P, Q;
+BEGIN
+	MOD := P - Q * (P / Q);
+END;
+
+%  RETURN GREATEST COMMON DIVISOR OF X AND Y  %
+INTEGER FUNCTION GCD (X, Y);
+INTEGER X, Y;
+BEGIN
+	INTEGER R;
+	IF X < Y THEN
+	BEGIN
+		INTEGER TEMP;
+		TEMP := X;
+		X := Y;
+		Y := TEMP;
+	END;
+	WHILE (R := MOD(X, Y)) <> 0 DO
+	BEGIN
+		X := Y;
+		Y := R;
+	END;
+	GCD := Y;
+END;
+
+% RETURN PHI (ALSO CALLED TOTIENT) OF N %
+INTEGER FUNCTION PHI(N);
+INTEGER N;
+BEGIN
+	INTEGER I, COUNT;
+        COUNT := 1;
+        FOR I := 2 STEP 1 UNTIL N DO
+	BEGIN
+		IF GCD(N,I) = 1 THEN COUNT := COUNT + 1;
+ 	END;
+	PHI := COUNT;
+END;
+
+
+COMMENT - EXERCISE THE FUNCTION;
+INTEGER N, TOTIENT, COUNT;
+WRITE("    N   PHI(N)  PRIME?");
+FOR N := 1 STEP 1 UNTIL 25 DO
+BEGIN
+        WRITE(N, (TOTIENT := PHI(N)));
+        WRITEON(IF TOTIENT = (N-1) THEN "   YES" ELSE "   NO");
+END;
+
+COMMENT - AND USE IT TO COUNT PRIMES;
+WRITE("");
+COUNT := 0;
+FOR N := 1 STEP 1 UNTIL 1000 DO
+BEGIN
+   	IF PHI(N) = (N-1) THEN COUNT := COUNT + 1;
+   	IF N = 100 THEN
+		WRITE("PRIMES UP TO 100 =", COUNT)
+        ELSE IF N = 1000 THEN
+		WRITE("PRIMES UP TO 1000 =", COUNT);
+END;
+
+
+END