update from Atlas with major reorg

attic/operator/Interest.java

@@ -0,0 +1,26 @@
+/***
+Compound interest function with ``BigDecimal``
+
+Equivalent in Python:
+
+    def compound_interest(principal, rate, periods):
+        return principal * ((1 + rate) ** periods - 1)
+
+***/
+
+import java.math.BigDecimal;
+
+public class Interest {
+
+    static BigDecimal compoundInterest(BigDecimal principal, BigDecimal rate, int periods) {
+        return principal.multiply(BigDecimal.ONE.add(rate).pow(periods).subtract(BigDecimal.ONE));
+    }
+
+    public static void main(String[] args) {
+        BigDecimal principal = new BigDecimal(1000);
+        BigDecimal rate = new BigDecimal("0.06");
+        int periods = 5;        
+        System.out.println(compoundInterest(principal, rate, periods));
+    }
+
+}