1 // ****************************************************************************** 2 // 3 // Title: Force Field X. 4 // Description: Force Field X - Software for Molecular Biophysics. 5 // Copyright: Copyright (c) Michael J. Schnieders 2001-2025. 6 // 7 // This file is part of Force Field X. 8 // 9 // Force Field X is free software; you can redistribute it and/or modify it 10 // under the terms of the GNU General Public License version 3 as published by 11 // the Free Software Foundation. 12 // 13 // Force Field X is distributed in the hope that it will be useful, but WITHOUT 14 // ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS 15 // FOR A PARTICULAR PURPOSE. See the GNU General Public License for more 16 // details. 17 // 18 // You should have received a copy of the GNU General Public License along with 19 // Force Field X; if not, write to the Free Software Foundation, Inc., 59 Temple 20 // Place, Suite 330, Boston, MA 02111-1307 USA 21 // 22 // Linking this library statically or dynamically with other modules is making a 23 // combined work based on this library. Thus, the terms and conditions of the 24 // GNU General Public License cover the whole combination. 25 // 26 // As a special exception, the copyright holders of this library give you 27 // permission to link this library with independent modules to produce an 28 // executable, regardless of the license terms of these independent modules, and 29 // to copy and distribute the resulting executable under terms of your choice, 30 // provided that you also meet, for each linked independent module, the terms 31 // and conditions of the license of that module. An independent module is a 32 // module which is not derived from or based on this library. If you modify this 33 // library, you may extend this exception to your version of the library, but 34 // you are not obligated to do so. If you do not wish to do so, delete this 35 // exception statement from your version. 36 // 37 // ****************************************************************************** 38 package ffx.numerics.switching; 39 40 import static java.lang.String.format; 41 42 /** 43 * The ConstantSwitch returns a constant value for all input values x. This is useful for having a 44 * single code path that accommodates both "real" switching behavior and no switching behavior. The 45 * default value is 1.0. 46 * 47 * @author Jacob M. Litman 48 * @author Michael J. Schnieders 49 */ 50 public class ConstantSwitch implements UnivariateSwitchingFunction { 51 52 private final double val; 53 54 /** Default constructor: constant 1.0 value. */ 55 public ConstantSwitch() { 56 this(1.0); 57 } 58 59 /** 60 * Permits specification of a value. 61 * 62 * @param value Value this ConstantSwitch should maintain. 63 */ 64 public ConstantSwitch(double value) { 65 this.val = value; 66 } 67 68 /** {@inheritDoc} */ 69 @Override 70 public boolean constantOutsideBounds() { 71 return true; 72 } 73 74 /** {@inheritDoc} */ 75 @Override 76 public double firstDerivative(double x) { 77 return 0.0; 78 } 79 80 /** {@inheritDoc} */ 81 @Override 82 public int getHighestOrderZeroDerivative() { 83 return 1; 84 } 85 86 /** {@inheritDoc} */ 87 @Override 88 public double getOneBound() { 89 return Double.NaN; 90 } 91 92 /** {@inheritDoc} */ 93 @Override 94 public double getZeroBound() { 95 return Double.NaN; 96 } 97 98 /** {@inheritDoc} */ 99 @Override 100 public double nthDerivative(double x, int order) throws IllegalArgumentException { 101 if (order < 0) { 102 throw new IllegalArgumentException(format(" Order must be > 0, was %d", order)); 103 } else if (order == 0) { 104 return val; 105 } 106 return 0.0; 107 } 108 109 /** {@inheritDoc} */ 110 @Override 111 public double secondDerivative(double x) { 112 return 0.0; 113 } 114 115 /** {@inheritDoc} */ 116 @Override 117 public boolean symmetricToUnity() { 118 return true; 119 } 120 121 @Override 122 public String toString() { 123 return format( 124 "Constant-value f(x) = %f, with no switching behavior (i.e. a dummy switch)", val); 125 } 126 127 /** {@inheritDoc} */ 128 @Override 129 public boolean validOutsideBounds() { 130 return false; 131 } 132 133 /** {@inheritDoc} */ 134 @Override 135 public double valueAt(double x) throws IllegalArgumentException { 136 return val; 137 } 138 }