summaryrefslogtreecommitdiff
path: root/indra/llcommon/llunit.h
blob: c60088360752e6897d25711612a7975b2018993c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
/** 
 * @file llunit.h
 * @brief Unit conversion classes
 *
 * $LicenseInfo:firstyear=2001&license=viewerlgpl$
 * Second Life Viewer Source Code
 * Copyright (C) 2012, Linden Research, Inc.
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation;
 * version 2.1 of the License only.
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 * 
 * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
 * $/LicenseInfo$
 */

#ifndef LL_LLUNIT_H
#define LL_LLUNIT_H

#include "stdtypes.h"
#include "llpreprocessor.h"
#include "llerrorlegacy.h"

namespace LLUnits
{

template<typename T>
struct HighestPrecisionType
{
	typedef T type_t;
};

template<> struct HighestPrecisionType<F32> { typedef F64 type_t; };
template<> struct HighestPrecisionType<S32> { typedef S64 type_t; };
template<> struct HighestPrecisionType<U32> { typedef S64 type_t; };
template<> struct HighestPrecisionType<S16> { typedef S64 type_t; };
template<> struct HighestPrecisionType<U16> { typedef S64 type_t; };
template<> struct HighestPrecisionType<S8> { typedef S64 type_t; };
template<> struct HighestPrecisionType<U8> { typedef S64 type_t; };

template<typename DERIVED_UNITS_TAG, typename BASE_UNITS_TAG, typename VALUE_TYPE>
struct ConversionFactor
{
	static typename HighestPrecisionType<VALUE_TYPE>::type_t get()
	{
		// spurious use of dependent type to stop gcc from triggering the static assertion before instantiating the template
		llstatic_assert_template(DERIVED_UNITS_TAG, false,  "Cannot convert between types.");
	}
};

template<typename BASE_UNITS_TAG, typename VALUE_TYPE>
struct ConversionFactor<BASE_UNITS_TAG, BASE_UNITS_TAG, VALUE_TYPE>
{
	static typename HighestPrecisionType<VALUE_TYPE>::type_t get() 
	{ 
		return 1; 
	}
};

}

template<typename UNIT_TYPE, typename STORAGE_TYPE>
struct LLUnit
{
	typedef LLUnit<UNIT_TYPE, STORAGE_TYPE> self_t;
	typedef STORAGE_TYPE storage_t;

	// value initialization
	LLUnit(storage_t value = storage_t())
	:	mValue(value)
	{}

	// unit initialization and conversion
	template<typename OTHER_UNIT, typename OTHER_STORAGE>
	LLUnit(LLUnit<OTHER_UNIT, OTHER_STORAGE> other)
	:	mValue(convert(other))
	{}
	
	// value assignment
	self_t& operator = (storage_t value)
	{
		mValue = value;
		return *this;
	}

	// unit assignment
	template<typename OTHER_UNIT, typename OTHER_STORAGE>
	self_t& operator = (LLUnit<OTHER_UNIT, OTHER_STORAGE> other)
	{
		mValue = convert(other);
		return *this;
	}

	storage_t value() const
	{
		return mValue;
	}

	template<typename NEW_UNIT_TYPE, typename NEW_STORAGE_TYPE> LLUnit<NEW_UNIT_TYPE, NEW_STORAGE_TYPE> as()
	{
		return LLUnit<NEW_UNIT_TYPE, NEW_STORAGE_TYPE>(*this);
	}

	void operator += (storage_t value)
	{
		mValue += value;
	}

	template<typename OTHER_UNIT, typename OTHER_STORAGE>
	void operator += (LLUnit<OTHER_UNIT, OTHER_STORAGE> other)
	{
		mValue += convert(other);
	}

	void operator -= (storage_t value)
	{
		mValue -= value;
	}

	template<typename OTHER_UNIT, typename OTHER_STORAGE>
	void operator -= (LLUnit<OTHER_UNIT, OTHER_STORAGE> other)
	{
		mValue -= convert(other);
	}

	void operator *= (storage_t multiplicand)
	{
		mValue *= multiplicand;
	}

	template<typename OTHER_UNIT, typename OTHER_STORAGE>
	void operator *= (LLUnit<OTHER_UNIT, OTHER_STORAGE> multiplicand)
	{
		// spurious use of dependent type to stop gcc from triggering the static assertion before instantiating the template
		llstatic_assert_template(OTHER_UNIT, 0, "Multiplication of unit types not supported.");
	}

	void operator /= (storage_t divisor)
	{
		mValue /= divisor;
	}

	template<typename OTHER_UNIT, typename OTHER_STORAGE>
	void operator /= (LLUnit<OTHER_UNIT, OTHER_STORAGE> divisor)
	{
		// spurious use of dependent type to stop gcc from triggering the static assertion before instantiating the template
		llstatic_assert_template(OTHER_UNIT, 0, "Illegal in-place division of unit types.");
	}

	template<typename SOURCE_UNITS, typename SOURCE_STORAGE>
	static storage_t convert(LLUnit<SOURCE_UNITS, SOURCE_STORAGE> v) 
	{ 
		return (storage_t)(v.value() 
			* LLUnits::ConversionFactor<SOURCE_UNITS, typename UNIT_TYPE::base_unit_t, SOURCE_STORAGE>::get() 
			* LLUnits::ConversionFactor<typename UNIT_TYPE::base_unit_t, UNIT_TYPE, STORAGE_TYPE>::get()); 
	}

protected:
	storage_t mValue;
};

template<typename UNIT_TYPE, typename STORAGE_TYPE>
struct LLUnitImplicit : public LLUnit<UNIT_TYPE, STORAGE_TYPE>
{
	typedef LLUnitImplicit<UNIT_TYPE, STORAGE_TYPE> self_t;
	typedef typename LLUnit<UNIT_TYPE, STORAGE_TYPE>::storage_t storage_t;
	typedef LLUnit<UNIT_TYPE, STORAGE_TYPE> base_t;

	LLUnitImplicit(storage_t value = storage_t())
	:	base_t(value)
	{}

	template<typename OTHER_UNIT, typename OTHER_STORAGE>
	LLUnitImplicit(LLUnit<OTHER_UNIT, OTHER_STORAGE> other)
	:	base_t(convert(other))
	{}

	// unlike LLUnit, LLUnitImplicit is *implicitly* convertable to a POD scalar (F32, S32, etc)
	// this allows for interoperability with legacy code
	operator storage_t() const
	{
		return base_t::value();
	}
};

//
// operator +
//
template<typename UNIT_TYPE1, typename STORAGE_TYPE1, typename UNIT_TYPE2, typename STORAGE_TYPE2>
LLUnit<UNIT_TYPE1, STORAGE_TYPE1> operator + (LLUnit<UNIT_TYPE1, STORAGE_TYPE1> first, LLUnit<UNIT_TYPE2, STORAGE_TYPE2> second)
{
	LLUnit<UNIT_TYPE1, STORAGE_TYPE1> result(first);
	result += second;
	return result;
}

template<typename UNIT_TYPE, typename STORAGE_TYPE, typename SCALAR_TYPE>
LLUnit<UNIT_TYPE, STORAGE_TYPE> operator + (LLUnit<UNIT_TYPE, STORAGE_TYPE> first, SCALAR_TYPE second)
{
	LLUnit<UNIT_TYPE, STORAGE_TYPE> result(first);
	result += second;
	return result;
}

template<typename UNIT_TYPE, typename STORAGE_TYPE, typename SCALAR_TYPE>
LLUnit<UNIT_TYPE, STORAGE_TYPE> operator + (SCALAR_TYPE first, LLUnit<UNIT_TYPE, STORAGE_TYPE> second)
{
	LLUnit<UNIT_TYPE, STORAGE_TYPE> result(first);
	result += second;
	return result;
}

template<typename UNIT_TYPE1, typename STORAGE_TYPE1, typename UNIT_TYPE2, typename STORAGE_TYPE2>
LLUnitImplicit<UNIT_TYPE1, STORAGE_TYPE1> operator + (LLUnitImplicit<UNIT_TYPE1, STORAGE_TYPE1> first, LLUnit<UNIT_TYPE2, STORAGE_TYPE2> second)
{
	LLUnitImplicit<UNIT_TYPE1, STORAGE_TYPE1> result(first);
	result += second;
	return result;
}

template<typename UNIT_TYPE, typename STORAGE_TYPE, typename SCALAR_TYPE>
LLUnitImplicit<UNIT_TYPE, STORAGE_TYPE> operator + (LLUnitImplicit<UNIT_TYPE, STORAGE_TYPE> first, SCALAR_TYPE second)
{
	LLUnitImplicit<UNIT_TYPE, STORAGE_TYPE> result(first);
	result += second;
	return result;
}

template<typename UNIT_TYPE1, typename STORAGE_TYPE1, typename UNIT_TYPE2, typename STORAGE_TYPE2>
LLUnitImplicit<UNIT_TYPE1, STORAGE_TYPE1> operator + (LLUnitImplicit<UNIT_TYPE1, STORAGE_TYPE1> first, LLUnitImplicit<UNIT_TYPE2, STORAGE_TYPE2> second)
{
	LLUnitImplicit<UNIT_TYPE1, STORAGE_TYPE1> result(first);
	result += second;
	return result;
}

//
// operator -
//
template<typename UNIT_TYPE1, typename STORAGE_TYPE1, typename UNIT_TYPE2, typename STORAGE_TYPE2>
LLUnit<UNIT_TYPE1, STORAGE_TYPE1> operator - (LLUnit<UNIT_TYPE1, STORAGE_TYPE1> first, LLUnit<UNIT_TYPE2, STORAGE_TYPE2> second)
{
	LLUnit<UNIT_TYPE1, STORAGE_TYPE1> result(first);
	result -= second;
	return result;
}

template<typename UNIT_TYPE, typename STORAGE_TYPE, typename SCALAR_TYPE>
LLUnit<UNIT_TYPE, STORAGE_TYPE> operator - (LLUnit<UNIT_TYPE, STORAGE_TYPE> first, SCALAR_TYPE second)
{
	LLUnit<UNIT_TYPE, STORAGE_TYPE> result(first);
	result -= second;
	return result;
}

template<typename UNIT_TYPE, typename STORAGE_TYPE, typename SCALAR_TYPE>
LLUnit<UNIT_TYPE, STORAGE_TYPE> operator - (SCALAR_TYPE first, LLUnit<UNIT_TYPE, STORAGE_TYPE> second)
{
	LLUnit<UNIT_TYPE, STORAGE_TYPE> result(first);
	result -= second;
	return result;
}

template<typename UNIT_TYPE1, typename STORAGE_TYPE1, typename UNIT_TYPE2, typename STORAGE_TYPE2>
LLUnitImplicit<UNIT_TYPE1, STORAGE_TYPE1> operator - (LLUnitImplicit<UNIT_TYPE1, STORAGE_TYPE1> first, LLUnitImplicit<UNIT_TYPE2, STORAGE_TYPE2> second)
{
	LLUnitImplicit<UNIT_TYPE1, STORAGE_TYPE1> result(first);
	result -= second;
	return result;
}

template<typename UNIT_TYPE, typename STORAGE_TYPE, typename SCALAR_TYPE>
LLUnitImplicit<UNIT_TYPE, STORAGE_TYPE> operator - (LLUnitImplicit<UNIT_TYPE, STORAGE_TYPE> first, SCALAR_TYPE second)
{
	LLUnitImplicit<UNIT_TYPE, STORAGE_TYPE> result(first);
	result -= second;
	return result;
}

template<typename UNIT_TYPE, typename STORAGE_TYPE, typename SCALAR_TYPE>
LLUnitImplicit<UNIT_TYPE, STORAGE_TYPE> operator - (SCALAR_TYPE first, LLUnitImplicit<UNIT_TYPE, STORAGE_TYPE> second)
{
	LLUnitImplicit<UNIT_TYPE, STORAGE_TYPE> result(first);
	result -= second;
	return result;
}

//
// operator *
//
template<typename UNIT_TYPE, typename STORAGE_TYPE, typename SCALAR_TYPE>
LLUnit<UNIT_TYPE, STORAGE_TYPE> operator * (SCALAR_TYPE first, LLUnit<UNIT_TYPE, STORAGE_TYPE> second)
{
	return LLUnit<UNIT_TYPE, STORAGE_TYPE>(first * second.value());
}

template<typename UNIT_TYPE, typename STORAGE_TYPE, typename SCALAR_TYPE>
LLUnit<UNIT_TYPE, STORAGE_TYPE> operator * (LLUnit<UNIT_TYPE, STORAGE_TYPE> first, SCALAR_TYPE second)
{
	return LLUnit<UNIT_TYPE, STORAGE_TYPE>(first.value() * second);
}

template<typename UNIT_TYPE1, typename STORAGE_TYPE1, typename UNIT_TYPE2, typename STORAGE_TYPE2>
LLUnit<UNIT_TYPE1, STORAGE_TYPE1> operator * (LLUnit<UNIT_TYPE1, STORAGE_TYPE1>, LLUnit<UNIT_TYPE2, STORAGE_TYPE2>)
{
	// spurious use of dependent type to stop gcc from triggering the static assertion before instantiating the template
	llstatic_assert_template(STORAGE_TYPE1, 0, "Multiplication of unit types results in new unit type - not supported.");
	return LLUnit<UNIT_TYPE1, STORAGE_TYPE1>();
}

template<typename UNIT_TYPE, typename STORAGE_TYPE, typename SCALAR_TYPE>
LLUnitImplicit<UNIT_TYPE, STORAGE_TYPE> operator * (SCALAR_TYPE first, LLUnitImplicit<UNIT_TYPE, STORAGE_TYPE> second)
{
	return LLUnitImplicit<UNIT_TYPE, STORAGE_TYPE>(first * second.value());
}

template<typename UNIT_TYPE, typename STORAGE_TYPE, typename SCALAR_TYPE>
LLUnitImplicit<UNIT_TYPE, STORAGE_TYPE> operator * (LLUnitImplicit<UNIT_TYPE, STORAGE_TYPE> first, SCALAR_TYPE second)
{
	return LLUnitImplicit<UNIT_TYPE, STORAGE_TYPE>(first.value() * second);
}

template<typename UNIT_TYPE1, typename STORAGE_TYPE1, typename UNIT_TYPE2, typename STORAGE_TYPE2>
LLUnitImplicit<UNIT_TYPE1, STORAGE_TYPE1> operator * (LLUnitImplicit<UNIT_TYPE1, STORAGE_TYPE1>, LLUnitImplicit<UNIT_TYPE2, STORAGE_TYPE2>)
{
	// spurious use of dependent type to stop gcc from triggering the static assertion before instantiating the template
	llstatic_assert_template(STORAGE_TYPE1, 0, "Multiplication of unit types results in new unit type - not supported.");
	return LLUnitImplicit<UNIT_TYPE1, STORAGE_TYPE1>();
}

//
// operator /
//
template<typename UNIT_TYPE, typename STORAGE_TYPE, typename SCALAR_TYPE>
SCALAR_TYPE operator / (SCALAR_TYPE first, LLUnit<UNIT_TYPE, STORAGE_TYPE> second)
{
	return SCALAR_TYPE(first / second.value());
}

template<typename UNIT_TYPE, typename STORAGE_TYPE, typename SCALAR_TYPE>
LLUnit<UNIT_TYPE, STORAGE_TYPE> operator / (LLUnit<UNIT_TYPE, STORAGE_TYPE> first, SCALAR_TYPE second)
{
	return LLUnit<UNIT_TYPE, STORAGE_TYPE>(first.value() / second);
}

template<typename UNIT_TYPE1, typename STORAGE_TYPE1, typename UNIT_TYPE2, typename STORAGE_TYPE2>
STORAGE_TYPE1 operator / (LLUnit<UNIT_TYPE1, STORAGE_TYPE1> first, LLUnit<UNIT_TYPE2, STORAGE_TYPE2> second)
{
	// spurious use of dependent type to stop gcc from triggering the static assertion before instantiating the template
	return STORAGE_TYPE1(first.value() / second.value());
}

template<typename UNIT_TYPE, typename STORAGE_TYPE, typename SCALAR_TYPE>
LLUnitImplicit<UNIT_TYPE, STORAGE_TYPE> operator / (LLUnitImplicit<UNIT_TYPE, STORAGE_TYPE> first, SCALAR_TYPE second)
{
	return LLUnitImplicit<UNIT_TYPE, STORAGE_TYPE>(first.value() / second);
}

template<typename UNIT_TYPE1, typename STORAGE_TYPE1, typename UNIT_TYPE2, typename STORAGE_TYPE2>
STORAGE_TYPE1 operator / (LLUnitImplicit<UNIT_TYPE1, STORAGE_TYPE1> first, LLUnitImplicit<UNIT_TYPE2, STORAGE_TYPE2> second)
{
	// spurious use of dependent type to stop gcc from triggering the static assertion before instantiating the template
	return STORAGE_TYPE1(first.value() / second.value());
}

#define COMPARISON_OPERATORS(op)                                                                                     \
template<typename UNIT_TYPE, typename STORAGE_TYPE, typename SCALAR_TYPE>                                            \
bool operator op (SCALAR_TYPE first, LLUnit<UNIT_TYPE, STORAGE_TYPE> second)                                         \
{                                                                                                                    \
	return first op second.value();                                                                                  \
}                                                                                                                    \
	                                                                                                                 \
template<typename UNIT_TYPE, typename STORAGE_TYPE, typename SCALAR_TYPE>                                            \
bool operator op (LLUnit<UNIT_TYPE, STORAGE_TYPE> first, SCALAR_TYPE second)                                         \
{                                                                                                                    \
	return first.value() op second;                                                                                  \
}                                                                                                                    \
	                                                                                                                 \
template<typename UNIT_TYPE1, typename STORAGE_TYPE1, typename UNIT_TYPE2, typename STORAGE_TYPE2>                   \
bool operator op (LLUnitImplicit<UNIT_TYPE1, STORAGE_TYPE1> first, LLUnitImplicit<UNIT_TYPE2, STORAGE_TYPE2> second) \
{                                                                                                                    \
	return first.value() op first.convert(second);                                                                   \
}                                                                                                                    \
	                                                                                                                 \
template<typename UNIT_TYPE1, typename STORAGE_TYPE1, typename UNIT_TYPE2, typename STORAGE_TYPE2>                   \
	bool operator op (LLUnit<UNIT_TYPE1, STORAGE_TYPE1> first, LLUnit<UNIT_TYPE2, STORAGE_TYPE2> second)             \
{                                                                                                                    \
	return first.value() op first.convert(second);                                                                   \
}

COMPARISON_OPERATORS(<)
COMPARISON_OPERATORS(<=)
COMPARISON_OPERATORS(>)
COMPARISON_OPERATORS(>=)
COMPARISON_OPERATORS(==)
COMPARISON_OPERATORS(!=)

namespace LLUnits
{
template<typename T>
T rawValue(T val) { return val; }

template<typename UNIT_TYPE, typename STORAGE_TYPE> 
STORAGE_TYPE rawValue(LLUnit<UNIT_TYPE, STORAGE_TYPE> val) { return val.value(); }

template<typename UNIT_TYPE, typename STORAGE_TYPE> 
STORAGE_TYPE rawValue(LLUnitImplicit<UNIT_TYPE, STORAGE_TYPE> val) { return val.value(); }

template<typename UNIT_TYPE, typename STORAGE_TYPE> 
struct HighestPrecisionType<LLUnit<UNIT_TYPE, STORAGE_TYPE> >
{
	typedef typename HighestPrecisionType<STORAGE_TYPE>::type_t type_t;
};

#define LL_DECLARE_DERIVED_UNIT(conversion_factor, base_unit_name, unit_name)                   \
struct unit_name                                                                                \
{                                                                                               \
	typedef base_unit_name base_unit_t;                                                         \
};                                                                                              \
template<typename STORAGE_TYPE>                                                                 \
struct ConversionFactor<unit_name, base_unit_name, STORAGE_TYPE>                                \
{                                                                                               \
	static typename HighestPrecisionType<STORAGE_TYPE>::type_t get()                            \
	{                                                                                           \
		return typename HighestPrecisionType<STORAGE_TYPE>::type_t(conversion_factor);          \
	}                                                                                           \
};                                                                                              \
	                                                                                            \
template<typename STORAGE_TYPE>                                                                 \
struct ConversionFactor<base_unit_name, unit_name, STORAGE_TYPE>						        \
{                                                                                               \
	static typename HighestPrecisionType<STORAGE_TYPE>::type_t get()                            \
	{                                                                                           \
		return typename HighestPrecisionType<STORAGE_TYPE>::type_t(1.0 / (conversion_factor));  \
	}                                                                                           \
}

struct Bytes { typedef Bytes base_unit_t; };
LL_DECLARE_DERIVED_UNIT(1024, Bytes, Kilobytes);
LL_DECLARE_DERIVED_UNIT(1024 * 1024, Bytes, Megabytes);
LL_DECLARE_DERIVED_UNIT(1024 * 1024 * 1024, Bytes, Gigabytes);
LL_DECLARE_DERIVED_UNIT(1.0 / 8.0, Bytes, Bits);
LL_DECLARE_DERIVED_UNIT(1024 / 8, Bytes, Kilobits);
LL_DECLARE_DERIVED_UNIT(1024 / 8, Bytes, Megabits);
LL_DECLARE_DERIVED_UNIT(1024 * 1024 * 1024 / 8, Bytes, Gigabits);

struct Seconds { typedef Seconds base_unit_t; };
LL_DECLARE_DERIVED_UNIT(60, Seconds, Minutes);
LL_DECLARE_DERIVED_UNIT(60 * 60, Seconds, Hours);
LL_DECLARE_DERIVED_UNIT(1.0 / 1000.0, Seconds, Milliseconds);
LL_DECLARE_DERIVED_UNIT(1.0 / 1000000.0, Seconds, Microseconds);
LL_DECLARE_DERIVED_UNIT(1.0 / 1000000000.0, Seconds, Nanoseconds);

struct Meters { typedef Meters base_unit_t; };
LL_DECLARE_DERIVED_UNIT(1000, Meters, Kilometers);
LL_DECLARE_DERIVED_UNIT(1.0 / 100.0, Meters, Centimeters);
LL_DECLARE_DERIVED_UNIT(1.0 / 1000.0, Meters, Millimeters);

struct Hertz { typedef Hertz base_unit_t; };
LL_DECLARE_DERIVED_UNIT(1000, Hertz, Kilohertz);
LL_DECLARE_DERIVED_UNIT(1000 * 1000, Hertz, Megahertz);
LL_DECLARE_DERIVED_UNIT(1000 * 1000 * 1000, Hertz, Gigahertz);
} // namespace LLUnits

#endif // LL_LLUNIT_H