first commit

java/expression/Sqrt.java

@@ -0,0 +1,60 @@
+package expression;
+
+import java.math.BigDecimal;
+import java.math.BigInteger;
+import java.util.List;
+
+/**
+ * @author Doschennikov Nikita (me@fymio.us)
+ */
+public class Sqrt extends AbstractExpression {
+    private final AbstractExpression operand;
+
+    public Sqrt(AbstractExpression operand) {
+        this.operand = operand;
+    }
+
+    private static int sqrtInt(int n) {
+        if (n < 0) throw new ArithmeticException("sqrt of negative number: " + n);
+        if (n == 0) return 0;
+        // Binary search: floor(sqrt(n)), result <= 46340 (sqrt(MAX_INT) < 46341)
+        int lo = 0, hi = 46340;
+        while (lo < hi) {
+            int mid = (lo + hi + 1) / 2;
+            if (mid * mid <= n) {
+                lo = mid;
+            } else {
+                hi = mid - 1;
+            }
+        }
+        return lo;
+    }
+
+    @Override public int        evaluate(int x)               { return sqrtInt(operand.evaluate(x)); }
+    @Override public int        evaluate(int x, int y, int z) { return sqrtInt(operand.evaluate(x,y,z)); }
+    @Override public int        evaluate(List<Integer> vars)  { return sqrtInt(operand.evaluate(vars)); }
+    @Override public BigInteger evaluateBi(List<BigInteger> vars) { return operand.evaluateBi(vars).sqrt(); }
+    @Override public BigDecimal evaluateBd(List<BigDecimal> vars) {
+        throw new UnsupportedOperationException("sqrt not supported for BigDecimal");
+    }
+
+    @Override public String toString()     { return "√(" + operand + ")"; }
+    // @Override public String toMiniString() { return "√" + operand.toMiniString(); }
+
+    @Override
+    public String toMiniString() {
+        if (operand instanceof AbstractBinaryOperation) {
+            return "√(" + operand.toMiniString() + ")";
+        }
+        return "√" + operand.toMiniString();
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) return true;
+        if (!(obj instanceof Sqrt)) return false;
+        return operand.equals(((Sqrt) obj).operand);
+    }
+
+    @Override public int hashCode() { return operand.hashCode() ^ 0x53515254; }
+}