Matt McCutchen's Web Site / measurements / measurements.git / blame
| Commit | Line | Data |
|---|---|---|
| 3f5430db MM |
1 | package net.mattmccutchen.measurements; |
| 2 | ||
| 3 | public class MeasurementMath { | |
| 4 | public static boolean unitsSame(Measurement a, Measurement b) { | |
| 5 | for (int i = 0; i < Unit.basicUnits.length; i++) | |
| 6 | if (a.unitPowers[i] != b.unitPowers[i]) | |
| 7 | return false; | |
| 8 | return true; | |
| 9 | } | |
| 10 | ||
| 11 | public static boolean isPureNumber(Measurement a) { | |
| 12 | for (int i = 0; i < Unit.basicUnits.length; i++) | |
| 13 | if (a.unitPowers[i] != 0) | |
| 14 | return false; | |
| 15 | return true; | |
| 16 | } | |
| 17 | ||
| 18 | public static Measurement neg(Measurement a) { | |
| 19 | if (a == null) | |
| 20 | return null; | |
| 21 | return new Measurement(-a.number, a.uncertainty, a.unitPowers); | |
| 22 | } | |
| 23 | ||
| 24 | public static Measurement add(Measurement a, Measurement b) { | |
| 25 | if (a == null || b == null || !unitsSame(a, b)) | |
| 26 | return null; | |
| 27 | return new Measurement(a.number + b.number, | |
| 28 | a.uncertainty + b.uncertainty, a.unitPowers); | |
| 29 | } | |
| 30 | ||
| 31 | public static Measurement sub(Measurement a, Measurement b) { | |
| 32 | if (a == null || b == null || !unitsSame(a, b)) | |
| 33 | return null; | |
| 34 | return new Measurement(a.number - b.number, | |
| 35 | a.uncertainty + b.uncertainty, a.unitPowers); | |
| 36 | } | |
| 37 | ||
| 38 | public static Measurement mul(Measurement a, Measurement b) { | |
| 39 | if (a == null || b == null) | |
| 40 | return null; | |
| 41 | int[] up = new int[Unit.basicUnits.length]; | |
| 42 | for (int i = 0; i < Unit.basicUnits.length; i++) | |
| 43 | up[i] = a.unitPowers[i] + b.unitPowers[i]; | |
| 44 | return new Measurement(a.number * b.number, | |
| 45 | a.uncertainty * Math.abs(b.number) | |
| 46 | + b.uncertainty * Math.abs(a.number), | |
| 47 | up); | |
| 48 | } | |
| 49 | ||
| 50 | public static Measurement div(Measurement a, Measurement b) { | |
| 51 | if (a == null || b == null) | |
| 52 | return null; | |
| 53 | int[] up = new int[Unit.basicUnits.length]; | |
| 54 | for (int i = 0; i < Unit.basicUnits.length; i++) | |
| 55 | up[i] = a.unitPowers[i] - b.unitPowers[i]; | |
| 56 | return new Measurement(a.number / b.number, | |
| 57 | // Compare to quotient rule for differentiation | |
| 58 | a.uncertainty / Math.abs(b.number) | |
| 59 | + Math.abs(a.number) * b.uncertainty / (b.number * b.number), | |
| 60 | up); | |
| 61 | } | |
| 62 | ||
| 63 | public static Measurement powint(Measurement a, int b) { | |
| 64 | if (a == null) | |
| 65 | return null; | |
| 66 | int[] up = new int[Unit.basicUnits.length]; | |
| 67 | for (int i = 0; i < Unit.basicUnits.length; i++) | |
| 68 | up[i] = a.unitPowers[i] * b; | |
| 69 | return new Measurement(Math.pow(a.number, b), | |
| 70 | b * a.uncertainty * Math.pow(a.number, b-1), | |
| 71 | up); | |
| 72 | } | |
| 73 | ||
| 74 | public static Measurement pow(Measurement a, Measurement b) { | |
| 75 | if (a == null || !isPureNumber(a) || b == null || !isPureNumber(b)) | |
| 76 | return null; | |
| 77 | return new Measurement(Math.pow(a.number, b.number), | |
| 78 | b.number * a.uncertainty * Math.pow(a.number, b.number-1) | |
| 79 | // think: derivative of e^(b ln a) is b' (ln a) e^(b ln a) | |
| 80 | + b.uncertainty * Math.log(a.number) * Math.pow(a.number, b.number), | |
| 81 | Measurement.pureNumberUnitPowers); | |
| 82 | } | |
| 83 | ||
| 84 | public static double cmp(Measurement a, Measurement b) { | |
| 85 | if (a == null || b == null || !unitsSame(a, b)) | |
| 86 | return Double.NaN; | |
| 87 | return (a.number - b.number) / (a.uncertainty + b.uncertainty); | |
| 88 | } | |
| 89 | } |