Data commit

Task/Additive-primes/Modula-2/additive-primes.mod2

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+MODULE AdditivePrimes;
+FROM InOut IMPORT WriteString, WriteCard, WriteLn;
+
+CONST
+    Max = 500;
+
+VAR
+    N: CARDINAL;
+    Count: CARDINAL;
+    Prime: ARRAY [2..Max] OF BOOLEAN;
+
+PROCEDURE DigitSum(n: CARDINAL): CARDINAL;
+BEGIN
+    IF n < 10 THEN
+        RETURN n;
+    ELSE
+        RETURN (n MOD 10) + DigitSum(n DIV 10);
+    END;
+END DigitSum;
+
+PROCEDURE Sieve;
+VAR i, j, max2: CARDINAL;
+BEGIN
+    FOR i := 2 TO Max DO
+        Prime[i] := TRUE;
+    END;
+
+    FOR i := 2 TO Max DIV 2 DO
+        IF Prime[i] THEN;
+            j := i*2;
+            WHILE j <= Max DO
+                Prime[j] := FALSE;
+                j := j + i;
+            END;
+        END;
+    END;
+END Sieve;
+
+BEGIN
+    Count := 0;
+    Sieve();
+    FOR N := 2 TO Max DO
+        IF Prime[N] AND Prime[DigitSum(N)] THEN
+            WriteCard(N, 4);
+            Count := Count + 1;
+            IF Count MOD 10 = 0 THEN WriteLn(); END;
+        END;
+    END;
+    WriteLn();
+    WriteString('There are '); WriteCard(Count,0);
+    WriteString(' additive primes less than '); WriteCard(Max,0);
+    WriteString('.');
+    WriteLn();
+END AdditivePrimes.