1// tUnits.h 
2// 
3// Definitions of various units for length, time, and mass along with the SI multiplier prefixes. 
4// 
5// Copyright (c) 2017, 2020 Tristan Grimmer. 
6// Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby 
7// granted, provided that the above copyright notice and this permission notice appear in all copies. 
8// 
9// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL 
10// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, 
11// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN 
12// AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR 
13// PERFORMANCE OF THIS SOFTWARE. 
14 
15#pragma once 
16 
17 
18namespace tUnit 
19{ 
20 // Conversion constants. 
21 // Prefixes (SI): 
22 // n=nano, u=micro, m=milli 
23 // K=kilo, M=mega, G=giga. 
24 // p=per 
25 // Units: 
26 // mi = mile. 
27 // m = meter. 
28 // L = litre. 
29 const float Conv_Km_per_mi = 1.609344f; 
30 const float Conv_Kmph_per_mps = 3.6f; 
31 
32 enum class tPrefix 
33 { 
34 Invalid = -1, 
35 
36 Yocto, // 10^-24 
37 Zepto, // 10^-21 
38 Atto, // 10^-18 
39 Femto, // 10^-15 
40 Pico, // 10^-12 
41 Nano, // 10^-9 
42 Micro, // 10^-6 
43 Milli, // 10^-3 
44 Centi, // 10^-2 
45 Deci, // 10^-1 
46 Unit, // 10^0 Not an SI prefix, but a handy one. 
47 Deca, // 10^1 
48 Hecto, // 10^2 
49 Kilo, // 10^3 
50 Mega, // 10^6 
51 Giga, // 10^9 
52 Tera, // 10^12 
53 Peta, // 10^15 
54 Exa, // 10^18 
55 Zetta, // 10^21 
56 Yotta, // 10^24 
57  
58 // Non SI prefixes. 
59 // Bi and Di are missing on purpose because they are ambiguous. In chemistry they both mean '2 of' like 
60 // sodium-BIcarbonate and carbon DIoxide, but sometimes they mean half. Never mind confusion about being paid 
61 // bi-monthly. Certainly semi-monthly is clear. Actually, we should look here for more: 
62 // https://en.wikipedia.org/wiki/Numeral_prefix like Duo, Quad, Sept, Hex, etc. 
63 Thrice, 
64 Twice, 
65 Semi, // Half of. 
66 Half, 
67 Quarter, 
68 Eighth, 
69 Sixteenth, 
70 Thirtysecondth, 
71 Sixtyfourth, 
72 
73 PrefixCount 
74 }; 
75  
76 enum class tTime 
77 { 
78 Unspecified = -1, 
79  
80 PlankTime, // 5.39E-44 seconds. 
81 Chronon, // 6.97E-24 seconds. Smallest indivisible unit?! 
82 
83 // These next 6 should perhaps not be here since we could use the tPrefix and Second units. Still, they are 
84 // common enough that perhaps they do deserve their own units. 
85 Attosecond, 
86 Femtosecond, 
87 Picosecond, 
88 Nanosecond, 
89 Microsecond, 
90 Millisecond, 
91  
92 Tick, // 1/60 of a second. 
93 Second, 
94 She, // Babylonian. 0.3 seconds. 
95 Helek, // Hebrew. Plural: halakim. 10/3 seconds. 
96 Minute, 
97 Hour, 
98 Day, // Precisely 24 hours. Not an Earth rotation 23h 59m 56s. 
99 Week, // Precisely 7 days. 
100 
101 Fortnight, // Precisely 2 weeks. 
102 // No months because they vary in duration. 
103 Year, // Precisely 365 canonical days. 
104 Annum, // Precisely 365 canonical days. 
105 Century, // 100 years. 
106 Millennium, // 1000 years. 
107 GalacticYear, // One GY is 250 million years. 
108  
109 NumTimeUnits 
110 }; 
111  
112 enum class tLength 
113 { 
114 Unspecified = -1, 
115 Angstrom, 
116 Meter, 
117 Kilometer, // Could use the tPrefix, but it's a common measure. 
118 Inch, 
119 Foot, 
120 Yard, 
121 Fathom, 
122 Mile, 
123 NauticalMile, 
124 AstronomicalUnit, 
125 NumLengthUnits 
126 }; 
127  
128 enum class tMass 
129 { 
130 Unspecified = -1, 
131 Gram, 
132 Kilogram, // Could use the tPrefix, but it's a common measure. 
133 Slug, 
134 NumMassUnits 
135 }; 
136  
137 // No compound units until we figure out how they'll work. For example, force (LBS, Newtons, etc) is composed of: 
138 // mass-unit * distance-unit / (time-unit * time-unit). 
139 
140 // These return pointers to persistent (static) char strings. They return nullptr if Unspecified is passed in. 
141 const char* GetUnitName(tTime); 
142 const char* GetUnitName(tLength); 
143 const char* GetUnitName(tMass); 
144 
145 // Given a unit name, these return the associated unit. Case insensitive compares, but no other fuzziness. They 
146 // return Unspecified if the name can't be found. 
147 tTime GetTimeUnit(const char* name); 
148 tLength GetLengthUnit(const char* name); 
149 tMass GetMassUnit(const char* name); 
150} 
151