added getExponent methods to FastMath

JIRA: MATH-497

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/trunk@1062368 13f79535-47bb-0310-9956-ffa450edef68

src/main/java/org/apache/commons/math/util/FastMath.java

@@ -29,9 +29,11 @@ package org.apache.commons.math.util;
  * The following methods are found in StrictMath since 1.6 only
  * <ul>
  * <li>{@link #copySign(double, double)}</li>
+ * <li>{@link #getExponent(double)}</li>
  * <li>{@link #nextAfter(double,double)}</li>
  * <li>{@link #nextUp(double)}</li>
  * <li>{@link #copySign(float, float)}</li>
+ * <li>{@link #getExponent(float)}</li>
  * <li>{@link #nextUp(float)}</li>
  * </ul>
  * @version $Revision$ $Date$
@@ -3760,4 +3762,31 @@ public class FastMath {
         }
         return -magnitude; // flip sign
     }
+
+    /**
+     * Return the exponent of a double number, removing the bias.
+     * <p>
+     * For double numbers of the form 2<sup>x</sup>, the unbiased
+     * exponent is exactly x.
+     * </p>
+     * @param d number from which exponent is requested
+     * @return exponent for d in IEEE754 representation, without bias
+     */
+    public static int getExponent(final double d) {
+        return (int) ((Double.doubleToLongBits(d) >>> 52) & 0x7ff) - 1023;
+    }
+
+    /**
+     * Return the exponent of a float number, removing the bias.
+     * <p>
+     * For float numbers of the form 2<sup>x</sup>, the unbiased
+     * exponent is exactly x.
+     * </p>
+     * @param f number from which exponent is requested
+     * @return exponent for d in IEEE754 representation, without bias
+     */
+    public static int getExponent(final float f) {
+        return (int) ((Float.floatToIntBits(f) >>> 23) & 0xff) - 127;
+    }
+
 }

src/site/xdoc/changes.xml

@@ -183,9 +183,13 @@ The <action> type attribute can be add,update,fix,remove.
       </action>
     </release>
     <release version="2.2" date="TBD" description="TBD">
+      <action dev="luc" type="fix" issue="MATH-497">
+          FastMath is not an exact replacement for StrictMath
+          (partially fixed) Add getExponent(double), getExponent(float)
+      </action>
       <action dev="sebb" type="fix" issue="MATH-496">
           FastMath is not an exact replacement for StrictMath
-          (partially fixed) Add copySign(float), copySign(float)
+          (partially fixed) Add copySign(double), copySign(float)
       </action>
       <action dev="luc" type="fix" issue="MATH-484">
           separate discrete event detection from adaptive step size handling in ODE solvers,