001 package edu.nrao.sss.astronomy;
002
003 import java.util.EnumSet;
004 import java.util.Set;
005
006 import edu.nrao.sss.util.EnumerationUtility;
007
008 /**
009 * The polarizations a single receptor can detect.
010 * <p>
011 * This enumeration has the same name, and most of the elements have the same
012 * names and are in the same order, as the corresponding
013 * <a href="http://almasw.hq.eso.org/almasw/bin/view/HLA/GeneratedEnums#PolarizationType">
014 * ALMA enumeration</a>. The one exception is the <tt>UNSPECIFIED</tt>
015 * element, which is not present in the ALMA specification.</p>
016 * <p>
017 * <b><u>References</u></b>
018 * <ul>
019 * <li><a href="http://scienceworld.wolfram.com/physics/StokesParameters.html">
020 * World of Physics</a></li>
021 * <li><a href="http://www.atnf.csiro.au/computing/software/atca_aips/node11.html">
022 * ATNF</a></li>
023 * <li><a href="http://en.wikipedia.org/wiki/Stokes_parameters">
024 * Wikipedia</a></li>
025 * <li><a href="http://www.optics.arizona.edu/jcwyant/JoseDiaz/Polarization-Circular.htm">
026 * University of Arizona</a> (there's a great 3D motion display here)</li>
027 * </ul></p>
028 * <b>Version Info:</b>
029 * <table style="margin-left:2em">
030 * <tr><td>$Revision: 1387 $</td></tr>
031 * <tr><td>$Date: 2008-06-27 16:17:41 -0600 (Fri, 27 Jun 2008) $</td></tr>
032 * <tr><td>$Author: dharland $ (last person to modify)</td></tr>
033 * </table></p>
034 *
035 * @author David M. Harland
036 * @since 2007-09-24
037 */
038 public enum PolarizationType
039 {
040 /** Right-handed circular polarization. */
041 R(Dir.CIRCULAR)
042 {
043 @Override public PolarizationType getOpposite() { return L; }
044 },
045
046 /** Left-handed circular polarization. */
047 L(Dir.CIRCULAR)
048 {
049 @Override public PolarizationType getOpposite() { return R; }
050 },
051
052 /** X-axis linear polarization. */
053 X(Dir.LINEAR)
054 {
055 @Override public PolarizationType getOpposite() { return Y; }
056 },
057
058 /** Y-axis linear polarization. */
059 Y(Dir.LINEAR)
060 {
061 @Override public PolarizationType getOpposite() { return X; }
062 },
063
064 /** Used when the polarization is unspecified or unknown. */
065 UNSPECIFIED(false)
066 {
067 @Override public boolean isCircular() { return false; }
068 @Override public boolean isLinear() { return false; }
069 };
070
071 private static interface Dir
072 {
073 static final boolean CIRCULAR = true;
074 static final boolean LINEAR = false;
075 }
076
077 private boolean circular;
078
079 /** Creates a new element. */
080 private PolarizationType(boolean isCircular)
081 {
082 circular = isCircular;
083 }
084
085 /**
086 * Returns <i>true</i> if this is a type of <i>circular</i> polarization.
087 * @return <i>true</i> if this is a type of <i>circular</i> polarization.
088 */
089 public boolean isCircular()
090 {
091 return circular;
092 }
093
094 /**
095 * Returns <i>true</i> if this is a type of <i>linear</i> polarization.
096 * @return <i>true</i> if this is a type of <i>linear</i> polarization.
097 */
098 public boolean isLinear()
099 {
100 return !isCircular();
101 }
102
103 /**
104 * Returns the opposite polarization.
105 * @return the opposite polarization.
106 */
107 public PolarizationType getOpposite()
108 {
109 return this; //will override for all but UNSPECIFIED
110 }
111
112 /**
113 * Returns the polarization type represented by {@code text}.
114 * <p>
115 * For details about the transformation, see
116 * {@link EnumerationUtility#enumFromString(Class, String)}.</p>
117 *
118 * @param text a text representation of a polarization type.
119 *
120 * @return the polarization type represented by {@code text}.
121 */
122 public static PolarizationType fromString(String text)
123 {
124 return EnumerationUtility.getSharedInstance()
125 .enumFromString(PolarizationType.class, text);
126 }
127
128 /**
129 * Returns the complete set of circular polarizations.
130 * @return the complete set of circular polarizations.
131 */
132 public static Set<PolarizationType> getCircularTypes()
133 {
134 EnumSet<PolarizationType> types = EnumSet.noneOf(PolarizationType.class);
135
136 for (PolarizationType p : PolarizationType.values())
137 if (p.isCircular())
138 types.add(p);
139
140 return types;
141 }
142
143 /**
144 * Returns the complete set of linear polarizations.
145 * @return the complete set of linear polarizations.
146 */
147 public static Set<PolarizationType> getLinearTypes()
148 {
149 EnumSet<PolarizationType> types = EnumSet.noneOf(PolarizationType.class);
150
151 for (PolarizationType p : PolarizationType.values())
152 if (p.isLinear())
153 types.add(p);
154
155 return types;
156 }
157 }