first commit

java/expression/Log2.java

@@ -0,0 +1,52 @@
+package expression;
+
+import java.math.BigDecimal;
+import java.math.BigInteger;
+import java.util.List;
+
+/**
+ * @author Doschennikov Nikita (me@fymio.us)
+ */
+public class Log2 extends AbstractExpression {
+    private final AbstractExpression operand;
+
+    public Log2(AbstractExpression operand) {
+        this.operand = operand;
+    }
+
+    private static int log2(int n) {
+        if (n <= 0) throw new ArithmeticException("log₂ of non-positive number: " + n);
+        int result = 0;
+        int v = n;
+        while (v > 1) {
+            v >>= 1;
+            result++;
+        }
+        return result;
+    }
+
+    @Override public int        evaluate(int x)               { return log2(operand.evaluate(x)); }
+    @Override public int        evaluate(int x, int y, int z) { return log2(operand.evaluate(x,y,z)); }
+    @Override public int        evaluate(List<Integer> vars)  { return log2(operand.evaluate(vars)); }
+    @Override public BigInteger evaluateBi(List<BigInteger> vars) { throw new UnsupportedOperationException(); }
+    @Override public BigDecimal evaluateBd(List<BigDecimal> vars) { throw new UnsupportedOperationException(); }
+
+    @Override public String toString()     { return "log₂(" + operand + ")"; }
+
+    @Override
+    public String toMiniString() {
+        if (operand instanceof AbstractBinaryOperation) {
+            return "log₂(" + operand.toMiniString() + ")";
+        }
+        return "log₂ " + operand.toMiniString();
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) return true;
+        if (!(obj instanceof Log2)) return false;
+        return operand.equals(((Log2) obj).operand);
+    }
+
+    @Override public int hashCode() { return operand.hashCode() ^ 0x4C4F4732; }
+}