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Units.hpp
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1 // This file is part of the Acts project.
2 //
3 // Copyright (C) 2016-2019 CERN for the benefit of the Acts project
4 //
5 // This Source Code Form is subject to the terms of the Mozilla Public
6 // License, v. 2.0. If a copy of the MPL was not distributed with this
7 // file, You can obtain one at http://mozilla.org/MPL/2.0/.
8 
9 #pragma once
10 
11 namespace Acts {
12 
84 
85 namespace UnitConstants {
86 // Length, native unit mm
87 constexpr double fm = 1e-12;
88 constexpr double pm = 1e-9;
89 constexpr double um = 1e-3;
90 constexpr double nm = 1e-6;
91 constexpr double mm = 1.0;
92 constexpr double cm = 10.0;
93 constexpr double m = 1e3;
94 constexpr double km = 1e6;
95 // Shortcuts for commonly used area and volume units. This intentionally
96 // contains not all possible combinations to avoid cluttering the namespace.
97 // Missing area or volume units can always be defined on the fly using the
98 // existing length units e.g. 1fm³ -> 1fm * 1fm * 1fm
99 // Area, native unit mm²
100 constexpr double mm2 = mm * mm;
101 constexpr double cm2 = cm * cm;
102 constexpr double m2 = m * m;
103 // Volume, native unit mm³
104 constexpr double mm3 = mm * mm * mm;
105 constexpr double cm3 = cm * cm * cm;
106 constexpr double m3 = m * m * m;
107 // Time, native unit mm = [speed-of-light * time] = mm/s * s
108 constexpr double s = 299792458000.0;
109 constexpr double fs = 1e-15 * s;
110 constexpr double ps = 1e-12 * s;
111 constexpr double ns = 1e-9 * s;
112 constexpr double us = 1e-6 * s;
113 constexpr double ms = 1e-3 * s;
114 constexpr double min = 60.0 * s;
115 constexpr double h = 3600.0 * s;
116 // Angles, native unit radian
117 constexpr double mrad = 1e-3;
118 constexpr double rad = 1.0;
119 constexpr double degree = 0.017453292519943295; // pi / 180
120 // Energy/mass/momentum, native unit GeV
121 constexpr double eV = 1e-9;
122 constexpr double keV = 1e-6;
123 constexpr double MeV = 1e-3;
124 constexpr double GeV = 1.0;
125 constexpr double TeV = 1e3;
126 // atomic mass unit u
127 constexpr double u = 0.93149410242;
128 // 1eV/c² == 1.782662e-36kg
129 // 1GeV/c² == 1.782662e-27kg
130 // -> 1kg == (1/1.782662e-27)GeV/c²
131 // -> 1g == (1/(1e3*1.782662e-27))GeV/c²
132 constexpr double g = 1.0 / 1.782662e-24;
133 constexpr double kg = 1.0 / 1.782662e-27;
134 // Charge, native unit e (elementary charge)
135 constexpr double e = 1.0;
136 constexpr double C = 1.602176634e19;
137 // Magnetic field, native unit GeV/(e*mm)
138 constexpr double T = 0.000299792458; // equivalent to c in appropriate SI units
139 constexpr double Gauss = 1e-4 * T;
140 constexpr double kGauss = 1e-1 * T;
141 } // namespace UnitConstants
142 
143 namespace UnitLiterals {
144 // define user literal functions for the given unit constant
145 #define ACTS_DEFINE_UNIT_LITERAL(name) \
146  constexpr double operator"" _##name(long double x) { \
147  return ::Acts::UnitConstants::name * x; \
148  } \
149  constexpr double operator"" _##name(unsigned long long x) { \
150  return ::Acts::UnitConstants::name * x; \
151  }
152 ACTS_DEFINE_UNIT_LITERAL(fm)
153 ACTS_DEFINE_UNIT_LITERAL(pm)
154 ACTS_DEFINE_UNIT_LITERAL(nm)
155 ACTS_DEFINE_UNIT_LITERAL(um)
156 ACTS_DEFINE_UNIT_LITERAL(mm)
157 ACTS_DEFINE_UNIT_LITERAL(cm)
158 ACTS_DEFINE_UNIT_LITERAL(m)
159 ACTS_DEFINE_UNIT_LITERAL(km)
160 ACTS_DEFINE_UNIT_LITERAL(mm2)
161 ACTS_DEFINE_UNIT_LITERAL(cm2)
162 ACTS_DEFINE_UNIT_LITERAL(m2)
163 ACTS_DEFINE_UNIT_LITERAL(mm3)
164 ACTS_DEFINE_UNIT_LITERAL(cm3)
165 ACTS_DEFINE_UNIT_LITERAL(m3)
166 ACTS_DEFINE_UNIT_LITERAL(fs)
167 ACTS_DEFINE_UNIT_LITERAL(ps)
168 ACTS_DEFINE_UNIT_LITERAL(ns)
169 ACTS_DEFINE_UNIT_LITERAL(us)
170 ACTS_DEFINE_UNIT_LITERAL(ms)
171 ACTS_DEFINE_UNIT_LITERAL(s)
172 ACTS_DEFINE_UNIT_LITERAL(min)
173 ACTS_DEFINE_UNIT_LITERAL(h)
174 ACTS_DEFINE_UNIT_LITERAL(mrad)
175 ACTS_DEFINE_UNIT_LITERAL(rad)
176 ACTS_DEFINE_UNIT_LITERAL(degree)
177 ACTS_DEFINE_UNIT_LITERAL(eV)
178 ACTS_DEFINE_UNIT_LITERAL(keV)
179 ACTS_DEFINE_UNIT_LITERAL(MeV)
180 ACTS_DEFINE_UNIT_LITERAL(GeV)
181 ACTS_DEFINE_UNIT_LITERAL(TeV)
182 ACTS_DEFINE_UNIT_LITERAL(u)
183 ACTS_DEFINE_UNIT_LITERAL(g)
184 ACTS_DEFINE_UNIT_LITERAL(kg)
185 ACTS_DEFINE_UNIT_LITERAL(e)
186 ACTS_DEFINE_UNIT_LITERAL(C)
187 ACTS_DEFINE_UNIT_LITERAL(T)
188 ACTS_DEFINE_UNIT_LITERAL(Gauss)
189 ACTS_DEFINE_UNIT_LITERAL(kGauss)
190 // not needed anymore. undef to prevent littering the namespace
191 #undef ACTS_DEFINE_UNIT_LITERAL
192 } // namespace UnitLiterals
193 
195 namespace units {
196 
199 constexpr double _km = UnitConstants::km;
200 constexpr double _m = UnitConstants::m;
201 constexpr double _cm = UnitConstants::cm;
202 constexpr double _mm = UnitConstants::mm;
203 constexpr double _um = UnitConstants::um;
204 constexpr double _nm = UnitConstants::nm;
205 constexpr double _pm = UnitConstants::pm;
206 constexpr double _fm = UnitConstants::fm;
208 constexpr double _mm2 = _mm * _mm;
210 
213 constexpr double _h = UnitConstants::h;
214 constexpr double _s = UnitConstants::s;
215 constexpr double _ms = UnitConstants::ms;
217 
220 constexpr double _GeV = UnitConstants::GeV;
221 constexpr double _TeV = UnitConstants::TeV;
222 constexpr double _MeV = UnitConstants::MeV;
223 constexpr double _keV = UnitConstants::keV;
224 constexpr double _eV = UnitConstants::eV;
225 constexpr double _g = UnitConstants::g;
226 constexpr double _kg = UnitConstants::kg;
228 
231 constexpr double _C = UnitConstants::C;
232 constexpr double _e = UnitConstants::e;
234 constexpr double _e2 = _e * _e;
236 
239 constexpr double _T = UnitConstants::T;
240 constexpr double _Gauss = UnitConstants::Gauss;
241 constexpr double _kGauss = UnitConstants::kGauss;
243 
244 } // namespace units
245 } // namespace Acts