tasks a-s

Task/Rot-13/Modula-3/rot-13.mod3

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+MODULE Rot13 EXPORTS Main;
+
+IMPORT Stdio, Rd, Wr;
+
+VAR c: CHAR;
+
+<*FATAL ANY*>
+
+BEGIN
+  WHILE NOT Rd.EOF(Stdio.stdin) DO
+    c := Rd.GetChar(Stdio.stdin);
+    IF c >= 'A' AND c <= 'M' OR c >= 'a' AND c <= 'm' THEN
+      c := VAL(ORD((ORD(c) + 13)), CHAR);
+    ELSIF c >= 'N' AND c <= 'Z' OR c >= 'n' AND c <= 'z' THEN
+      c := VAL(ORD((ORD(c) - 13)), CHAR);
+    END;
+    Wr.PutChar(Stdio.stdout, c);
+  END;
+END Rot13.