summaryrefslogtreecommitdiff
path: root/graphics/asymptote/optional.hpp
blob: 86e3b407c66e6f5aa41f549726ec82305d289f6d (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
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
//
// Copyright (c) 2014-2021 Martin Moene
//
// https://github.com/martinmoene/optional-lite
//
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

#pragma once

#ifndef NONSTD_OPTIONAL_LITE_HPP
#define NONSTD_OPTIONAL_LITE_HPP

#define optional_lite_MAJOR  3
#define optional_lite_MINOR  5
#define optional_lite_PATCH  0

#define optional_lite_VERSION  optional_STRINGIFY(optional_lite_MAJOR) "." optional_STRINGIFY(optional_lite_MINOR) "." optional_STRINGIFY(optional_lite_PATCH)

#define optional_STRINGIFY(  x )  optional_STRINGIFY_( x )
#define optional_STRINGIFY_( x )  #x

// optional-lite configuration:

#define optional_OPTIONAL_DEFAULT  0
#define optional_OPTIONAL_NONSTD   1
#define optional_OPTIONAL_STD      2

// tweak header support:

#ifdef __has_include
# if __has_include(<nonstd/optional.tweak.hpp>)
#  include <nonstd/optional.tweak.hpp>
# endif
#define optional_HAVE_TWEAK_HEADER  1
#else
#define optional_HAVE_TWEAK_HEADER  0
//# pragma message("optional.hpp: Note: Tweak header not supported.")
#endif

// optional selection and configuration:

#if !defined( optional_CONFIG_SELECT_OPTIONAL )
# define optional_CONFIG_SELECT_OPTIONAL  ( optional_HAVE_STD_OPTIONAL ? optional_OPTIONAL_STD : optional_OPTIONAL_NONSTD )
#endif

// Control presence of extensions:

#ifndef optional_CONFIG_NO_EXTENSIONS
#define optional_CONFIG_NO_EXTENSIONS  0
#endif

// Control presence of exception handling (try and auto discover):

#ifndef optional_CONFIG_NO_EXCEPTIONS
# if defined(_MSC_VER)
# include <cstddef>     // for _HAS_EXCEPTIONS
# endif
# if defined(__cpp_exceptions) || defined(__EXCEPTIONS) || (_HAS_EXCEPTIONS)
#  define optional_CONFIG_NO_EXCEPTIONS  0
# else
#  define optional_CONFIG_NO_EXCEPTIONS  1
# endif
#endif

// C++ language version detection (C++20 is speculative):
// Note: VC14.0/1900 (VS2015) lacks too much from C++14.

#ifndef   optional_CPLUSPLUS
# if defined(_MSVC_LANG ) && !defined(__clang__)
#  define optional_CPLUSPLUS  (_MSC_VER == 1900 ? 201103L : _MSVC_LANG )
# else
#  define optional_CPLUSPLUS  __cplusplus
# endif
#endif

#define optional_CPP98_OR_GREATER  ( optional_CPLUSPLUS >= 199711L )
#define optional_CPP11_OR_GREATER  ( optional_CPLUSPLUS >= 201103L )
#define optional_CPP11_OR_GREATER_ ( optional_CPLUSPLUS >= 201103L )
#define optional_CPP14_OR_GREATER  ( optional_CPLUSPLUS >= 201402L )
#define optional_CPP17_OR_GREATER  ( optional_CPLUSPLUS >= 201703L )
#define optional_CPP20_OR_GREATER  ( optional_CPLUSPLUS >= 202000L )

// C++ language version (represent 98 as 3):

#define optional_CPLUSPLUS_V  ( optional_CPLUSPLUS / 100 - (optional_CPLUSPLUS > 200000 ? 2000 : 1994) )

// Use C++17 std::optional if available and requested:

#if optional_CPP17_OR_GREATER && defined(__has_include )
# if __has_include( <optional> )
#  define optional_HAVE_STD_OPTIONAL  1
# else
#  define optional_HAVE_STD_OPTIONAL  0
# endif
#else
# define  optional_HAVE_STD_OPTIONAL  0
#endif

#define optional_USES_STD_OPTIONAL  ( (optional_CONFIG_SELECT_OPTIONAL == optional_OPTIONAL_STD) || ((optional_CONFIG_SELECT_OPTIONAL == optional_OPTIONAL_DEFAULT) && optional_HAVE_STD_OPTIONAL) )

//
// in_place: code duplicated in any-lite, expected-lite, optional-lite, value-ptr-lite, variant-lite:
//

#ifndef nonstd_lite_HAVE_IN_PLACE_TYPES
#define nonstd_lite_HAVE_IN_PLACE_TYPES  1

// C++17 std::in_place in <utility>:

#if optional_CPP17_OR_GREATER

#include <utility>

namespace nonstd {

using std::in_place;
using std::in_place_type;
using std::in_place_index;
using std::in_place_t;
using std::in_place_type_t;
using std::in_place_index_t;

#define nonstd_lite_in_place_t(      T)  std::in_place_t
#define nonstd_lite_in_place_type_t( T)  std::in_place_type_t<T>
#define nonstd_lite_in_place_index_t(K)  std::in_place_index_t<K>

#define nonstd_lite_in_place(      T)    std::in_place_t{}
#define nonstd_lite_in_place_type( T)    std::in_place_type_t<T>{}
#define nonstd_lite_in_place_index(K)    std::in_place_index_t<K>{}

} // namespace nonstd

#else // optional_CPP17_OR_GREATER

#include <cstddef>

namespace nonstd {
namespace detail {

template< class T >
struct in_place_type_tag {};

template< std::size_t K >
struct in_place_index_tag {};

} // namespace detail

struct in_place_t {};

template< class T >
inline in_place_t in_place( detail::in_place_type_tag<T> /*unused*/ = detail::in_place_type_tag<T>() )
{
    return in_place_t();
}

template< std::size_t K >
inline in_place_t in_place( detail::in_place_index_tag<K> /*unused*/ = detail::in_place_index_tag<K>() )
{
    return in_place_t();
}

template< class T >
inline in_place_t in_place_type( detail::in_place_type_tag<T> /*unused*/ = detail::in_place_type_tag<T>() )
{
    return in_place_t();
}

template< std::size_t K >
inline in_place_t in_place_index( detail::in_place_index_tag<K> /*unused*/ = detail::in_place_index_tag<K>() )
{
    return in_place_t();
}

// mimic templated typedef:

#define nonstd_lite_in_place_t(      T)  nonstd::in_place_t(&)( nonstd::detail::in_place_type_tag<T>  )
#define nonstd_lite_in_place_type_t( T)  nonstd::in_place_t(&)( nonstd::detail::in_place_type_tag<T>  )
#define nonstd_lite_in_place_index_t(K)  nonstd::in_place_t(&)( nonstd::detail::in_place_index_tag<K> )

#define nonstd_lite_in_place(      T)    nonstd::in_place_type<T>
#define nonstd_lite_in_place_type( T)    nonstd::in_place_type<T>
#define nonstd_lite_in_place_index(K)    nonstd::in_place_index<K>

} // namespace nonstd

#endif // optional_CPP17_OR_GREATER
#endif // nonstd_lite_HAVE_IN_PLACE_TYPES

//
// Using std::optional:
//

#if optional_USES_STD_OPTIONAL

#include <optional>

namespace nonstd {

    using std::optional;
    using std::bad_optional_access;
    using std::hash;

    using std::nullopt;
    using std::nullopt_t;

    using std::operator==;
    using std::operator!=;
    using std::operator<;
    using std::operator<=;
    using std::operator>;
    using std::operator>=;
    using std::make_optional;
    using std::swap;
}

#else // optional_USES_STD_OPTIONAL

#include <cassert>
#include <utility>

// optional-lite alignment configuration:

#ifndef  optional_CONFIG_MAX_ALIGN_HACK
# define optional_CONFIG_MAX_ALIGN_HACK  0
#endif

#ifndef  optional_CONFIG_ALIGN_AS
// no default, used in #if defined()
#endif

#ifndef  optional_CONFIG_ALIGN_AS_FALLBACK
# define optional_CONFIG_ALIGN_AS_FALLBACK  double
#endif

// Compiler warning suppression:

#if defined(__clang__)
# pragma clang diagnostic push
# pragma clang diagnostic ignored "-Wundef"
#elif defined(__GNUC__)
# pragma GCC   diagnostic push
# pragma GCC   diagnostic ignored "-Wundef"
#elif defined(_MSC_VER )
# pragma warning( push )
#endif

// half-open range [lo..hi):
#define optional_BETWEEN( v, lo, hi ) ( (lo) <= (v) && (v) < (hi) )

// Compiler versions:
//
// MSVC++  6.0  _MSC_VER == 1200  optional_COMPILER_MSVC_VERSION ==  60  (Visual Studio 6.0)
// MSVC++  7.0  _MSC_VER == 1300  optional_COMPILER_MSVC_VERSION ==  70  (Visual Studio .NET 2002)
// MSVC++  7.1  _MSC_VER == 1310  optional_COMPILER_MSVC_VERSION ==  71  (Visual Studio .NET 2003)
// MSVC++  8.0  _MSC_VER == 1400  optional_COMPILER_MSVC_VERSION ==  80  (Visual Studio 2005)
// MSVC++  9.0  _MSC_VER == 1500  optional_COMPILER_MSVC_VERSION ==  90  (Visual Studio 2008)
// MSVC++ 10.0  _MSC_VER == 1600  optional_COMPILER_MSVC_VERSION == 100  (Visual Studio 2010)
// MSVC++ 11.0  _MSC_VER == 1700  optional_COMPILER_MSVC_VERSION == 110  (Visual Studio 2012)
// MSVC++ 12.0  _MSC_VER == 1800  optional_COMPILER_MSVC_VERSION == 120  (Visual Studio 2013)
// MSVC++ 14.0  _MSC_VER == 1900  optional_COMPILER_MSVC_VERSION == 140  (Visual Studio 2015)
// MSVC++ 14.1  _MSC_VER >= 1910  optional_COMPILER_MSVC_VERSION == 141  (Visual Studio 2017)
// MSVC++ 14.2  _MSC_VER >= 1920  optional_COMPILER_MSVC_VERSION == 142  (Visual Studio 2019)

#if defined(_MSC_VER ) && !defined(__clang__)
# define optional_COMPILER_MSVC_VER      (_MSC_VER )
# define optional_COMPILER_MSVC_VERSION  (_MSC_VER / 10 - 10 * ( 5 + (_MSC_VER < 1900 ) ) )
#else
# define optional_COMPILER_MSVC_VER      0
# define optional_COMPILER_MSVC_VERSION  0
#endif

#define optional_COMPILER_VERSION( major, minor, patch )  ( 10 * (10 * (major) + (minor) ) + (patch) )

#if defined(__GNUC__) && !defined(__clang__)
# define optional_COMPILER_GNUC_VERSION   optional_COMPILER_VERSION(__GNUC__, __GNUC_MINOR__, __GNUC_PATCHLEVEL__)
#else
# define optional_COMPILER_GNUC_VERSION   0
#endif

#if defined(__clang__)
# define optional_COMPILER_CLANG_VERSION  optional_COMPILER_VERSION(__clang_major__, __clang_minor__, __clang_patchlevel__)
#else
# define optional_COMPILER_CLANG_VERSION  0
#endif

#if optional_BETWEEN(optional_COMPILER_MSVC_VERSION, 70, 140 )
# pragma warning( disable: 4345 )   // initialization behavior changed
#endif

#if optional_BETWEEN(optional_COMPILER_MSVC_VERSION, 70, 150 )
# pragma warning( disable: 4814 )   // in C++14 'constexpr' will not imply 'const'
#endif

// Presence of language and library features:

#define optional_HAVE(FEATURE) ( optional_HAVE_##FEATURE )

#ifdef _HAS_CPP0X
# define optional_HAS_CPP0X  _HAS_CPP0X
#else
# define optional_HAS_CPP0X  0
#endif

// Unless defined otherwise below, consider VC14 as C++11 for optional-lite:

#if optional_COMPILER_MSVC_VER >= 1900
# undef  optional_CPP11_OR_GREATER
# define optional_CPP11_OR_GREATER  1
#endif

#define optional_CPP11_90   (optional_CPP11_OR_GREATER_ || optional_COMPILER_MSVC_VER >= 1500)
#define optional_CPP11_100  (optional_CPP11_OR_GREATER_ || optional_COMPILER_MSVC_VER >= 1600)
#define optional_CPP11_110  (optional_CPP11_OR_GREATER_ || optional_COMPILER_MSVC_VER >= 1700)
#define optional_CPP11_120  (optional_CPP11_OR_GREATER_ || optional_COMPILER_MSVC_VER >= 1800)
#define optional_CPP11_140  (optional_CPP11_OR_GREATER_ || optional_COMPILER_MSVC_VER >= 1900)
#define optional_CPP11_141  (optional_CPP11_OR_GREATER_ || optional_COMPILER_MSVC_VER >= 1910)

#define optional_CPP14_000  (optional_CPP14_OR_GREATER)
#define optional_CPP17_000  (optional_CPP17_OR_GREATER)

// clang >= 2.9, gcc >= 4.9, msvc >= vc14.0/1900 (vs15):
#define optional_CPP11_140_C290_G490    ((optional_CPP11_OR_GREATER_ && (optional_COMPILER_CLANG_VERSION >= 290 || optional_COMPILER_GNUC_VERSION >= 490)) || (optional_COMPILER_MSVC_VER >= 1900))

// clang >= 3.5, msvc >= vc11 (vs12):
#define optional_CPP11_110_C350         ( optional_CPP11_110 && !optional_BETWEEN( optional_COMPILER_CLANG_VERSION, 1, 350 ) )

// clang >= 3.5, gcc >= 5.0, msvc >= vc11 (vs12):
#define optional_CPP11_110_C350_G500 \
    (  optional_CPP11_110 && \
    !( optional_BETWEEN( optional_COMPILER_CLANG_VERSION, 1, 350 ) \
    || optional_BETWEEN( optional_COMPILER_GNUC_VERSION , 1, 500 ) ) )

// Presence of C++11 language features:

#define optional_HAVE_CONSTEXPR_11      optional_CPP11_140
#define optional_HAVE_IS_DEFAULT        optional_CPP11_140
#define optional_HAVE_NOEXCEPT          optional_CPP11_140
#define optional_HAVE_NULLPTR           optional_CPP11_100
#define optional_HAVE_REF_QUALIFIER     optional_CPP11_140_C290_G490
#define optional_HAVE_STATIC_ASSERT     optional_CPP11_110
#define optional_HAVE_INITIALIZER_LIST  optional_CPP11_140

// Presence of C++14 language features:

#define optional_HAVE_CONSTEXPR_14      optional_CPP14_000

// Presence of C++17 language features:

#define optional_HAVE_NODISCARD         optional_CPP17_000

// Presence of C++ library features:

#define optional_HAVE_CONDITIONAL       optional_CPP11_120
#define optional_HAVE_REMOVE_CV         optional_CPP11_120
#define optional_HAVE_TYPE_TRAITS       optional_CPP11_90

#define optional_HAVE_TR1_TYPE_TRAITS   (!! optional_COMPILER_GNUC_VERSION )
#define optional_HAVE_TR1_ADD_POINTER   (!! optional_COMPILER_GNUC_VERSION )

#define optional_HAVE_IS_ASSIGNABLE                     optional_CPP11_110_C350
#define optional_HAVE_IS_MOVE_CONSTRUCTIBLE             optional_CPP11_110_C350
#define optional_HAVE_IS_NOTHROW_MOVE_ASSIGNABLE        optional_CPP11_110_C350
#define optional_HAVE_IS_NOTHROW_MOVE_CONSTRUCTIBLE     optional_CPP11_110_C350
#define optional_HAVE_IS_TRIVIALLY_COPY_CONSTRUCTIBLE   optional_CPP11_110_C350_G500
#define optional_HAVE_IS_TRIVIALLY_MOVE_CONSTRUCTIBLE   optional_CPP11_110_C350_G500

// C++ feature usage:

#if optional_HAVE( CONSTEXPR_11 )
# define optional_constexpr  constexpr
#else
# define optional_constexpr  /*constexpr*/
#endif

#if optional_HAVE( IS_DEFAULT )
# define optional_is_default  = default;
#else
# define optional_is_default  {}
#endif

#if optional_HAVE( CONSTEXPR_14 )
# define optional_constexpr14  constexpr
#else
# define optional_constexpr14  /*constexpr*/
#endif

#if optional_HAVE( NODISCARD )
# define optional_nodiscard  [[nodiscard]]
#else
# define optional_nodiscard  /*[[nodiscard]]*/
#endif

#if optional_HAVE( NOEXCEPT )
# define optional_noexcept  noexcept
#else
# define optional_noexcept  /*noexcept*/
#endif

#if optional_HAVE( NULLPTR )
# define optional_nullptr  nullptr
#else
# define optional_nullptr  NULL
#endif

#if optional_HAVE( REF_QUALIFIER )
// NOLINTNEXTLINE( bugprone-macro-parentheses )
# define optional_ref_qual  &
# define optional_refref_qual  &&
#else
# define optional_ref_qual  /*&*/
# define optional_refref_qual  /*&&*/
#endif

#if optional_HAVE( STATIC_ASSERT )
# define optional_static_assert(expr, text)    static_assert(expr, text);
#else
# define optional_static_assert(expr, text)  /*static_assert(expr, text);*/
#endif

// additional includes:

#if optional_CONFIG_NO_EXCEPTIONS
// already included: <cassert>
#else
# include <stdexcept>
#endif

#if optional_CPP11_OR_GREATER
# include <functional>
#endif

#if optional_HAVE( INITIALIZER_LIST )
# include <initializer_list>
#endif

#if optional_HAVE( TYPE_TRAITS )
# include <type_traits>
#elif optional_HAVE( TR1_TYPE_TRAITS )
# include <tr1/type_traits>
#endif

// Method enabling

#if optional_CPP11_OR_GREATER

#define optional_REQUIRES_0(...) \
    template< bool B = (__VA_ARGS__), typename std::enable_if<B, int>::type = 0 >

#define optional_REQUIRES_T(...) \
    , typename std::enable_if< (__VA_ARGS__), int >::type = 0

#define optional_REQUIRES_R(R, ...) \
    typename std::enable_if< (__VA_ARGS__), R>::type

#define optional_REQUIRES_A(...) \
    , typename std::enable_if< (__VA_ARGS__), void*>::type = nullptr

#endif

//
// optional:
//

namespace nonstd { namespace optional_lite {

namespace std11 {

template< class T, T v > struct integral_constant { enum { value = v }; };
template< bool B       > struct bool_constant : integral_constant<bool, B>{};

typedef bool_constant< true  > true_type;
typedef bool_constant< false > false_type;

#if optional_CPP11_OR_GREATER
    using std::move;
#else
    template< typename T > T & move( T & t ) { return t; }
#endif

#if optional_HAVE( CONDITIONAL )
    using std::conditional;
#else
    template< bool B, typename T, typename F > struct conditional              { typedef T type; };
    template<         typename T, typename F > struct conditional<false, T, F> { typedef F type; };
#endif // optional_HAVE_CONDITIONAL

#if optional_HAVE( IS_ASSIGNABLE )
    using std::is_assignable;
#else
    template< class T, class U > struct is_assignable : std11::true_type{};
#endif

#if optional_HAVE( IS_MOVE_CONSTRUCTIBLE )
    using std::is_move_constructible;
#else
    template< class T > struct is_move_constructible : std11::true_type{};
#endif

#if optional_HAVE( IS_NOTHROW_MOVE_ASSIGNABLE )
    using std::is_nothrow_move_assignable;
#else
    template< class T > struct is_nothrow_move_assignable : std11::true_type{};
#endif

#if optional_HAVE( IS_NOTHROW_MOVE_CONSTRUCTIBLE )
    using std::is_nothrow_move_constructible;
#else
    template< class T > struct is_nothrow_move_constructible : std11::true_type{};
#endif

#if optional_HAVE( IS_TRIVIALLY_COPY_CONSTRUCTIBLE )
    using std::is_trivially_copy_constructible;
#else
    template< class T > struct is_trivially_copy_constructible : std11::true_type{};
#endif

#if optional_HAVE( IS_TRIVIALLY_MOVE_CONSTRUCTIBLE )
    using std::is_trivially_move_constructible;
#else
    template< class T > struct is_trivially_move_constructible : std11::true_type{};
#endif

} // namespace std11

#if optional_CPP11_OR_GREATER

/// type traits C++17:

namespace std17 {

#if optional_CPP17_OR_GREATER

using std::is_swappable;
using std::is_nothrow_swappable;

#elif optional_CPP11_OR_GREATER

namespace detail {

using std::swap;

struct is_swappable
{
    template< typename T, typename = decltype( swap( std::declval<T&>(), std::declval<T&>() ) ) >
    static std11::true_type test( int /*unused*/ );

    template< typename >
    static std11::false_type test(...);
};

struct is_nothrow_swappable
{
    // wrap noexcept(expr) in separate function as work-around for VC140 (VS2015):

    template< typename T >
    static constexpr bool satisfies()
    {
        return noexcept( swap( std::declval<T&>(), std::declval<T&>() ) );
    }

    template< typename T >
    static auto test( int /*unused*/ ) -> std11::integral_constant<bool, satisfies<T>()>{}

    template< typename >
    static auto test(...) -> std11::false_type;
};

} // namespace detail

// is [nothow] swappable:

template< typename T >
struct is_swappable : decltype( detail::is_swappable::test<T>(0) ){};

template< typename T >
struct is_nothrow_swappable : decltype( detail::is_nothrow_swappable::test<T>(0) ){};

#endif // optional_CPP17_OR_GREATER

} // namespace std17

/// type traits C++20:

namespace std20 {

template< typename T >
struct remove_cvref
{
    typedef typename std::remove_cv< typename std::remove_reference<T>::type >::type type;
};

} // namespace std20

#endif // optional_CPP11_OR_GREATER

/// class optional

template< typename T >
class optional;

namespace detail {

// C++11 emulation:

struct nulltype{};

template< typename Head, typename Tail >
struct typelist
{
    typedef Head head;
    typedef Tail tail;
};

#if optional_CONFIG_MAX_ALIGN_HACK

// Max align, use most restricted type for alignment:

#define optional_UNIQUE(  name )       optional_UNIQUE2( name, __LINE__ )
#define optional_UNIQUE2( name, line ) optional_UNIQUE3( name, line )
#define optional_UNIQUE3( name, line ) name ## line

#define optional_ALIGN_TYPE( type ) \
    type optional_UNIQUE( _t ); struct_t< type > optional_UNIQUE( _st )

template< typename T >
struct struct_t { T _; };

union max_align_t
{
    optional_ALIGN_TYPE( char );
    optional_ALIGN_TYPE( short int );
    optional_ALIGN_TYPE( int );
    optional_ALIGN_TYPE( long int  );
    optional_ALIGN_TYPE( float  );
    optional_ALIGN_TYPE( double );
    optional_ALIGN_TYPE( long double );
    optional_ALIGN_TYPE( char * );
    optional_ALIGN_TYPE( short int * );
    optional_ALIGN_TYPE( int *  );
    optional_ALIGN_TYPE( long int * );
    optional_ALIGN_TYPE( float * );
    optional_ALIGN_TYPE( double * );
    optional_ALIGN_TYPE( long double * );
    optional_ALIGN_TYPE( void * );

#ifdef HAVE_LONG_LONG
    optional_ALIGN_TYPE( long long );
#endif

    struct Unknown;

    Unknown ( * optional_UNIQUE(_) )( Unknown );
    Unknown * Unknown::* optional_UNIQUE(_);
    Unknown ( Unknown::* optional_UNIQUE(_) )( Unknown );

    struct_t< Unknown ( * )( Unknown)         > optional_UNIQUE(_);
    struct_t< Unknown * Unknown::*            > optional_UNIQUE(_);
    struct_t< Unknown ( Unknown::* )(Unknown) > optional_UNIQUE(_);
};

#undef optional_UNIQUE
#undef optional_UNIQUE2
#undef optional_UNIQUE3

#undef optional_ALIGN_TYPE

#elif defined( optional_CONFIG_ALIGN_AS ) // optional_CONFIG_MAX_ALIGN_HACK

// Use user-specified type for alignment:

#define optional_ALIGN_AS( unused ) \
    optional_CONFIG_ALIGN_AS

#else // optional_CONFIG_MAX_ALIGN_HACK

// Determine POD type to use for alignment:

#define optional_ALIGN_AS( to_align ) \
    typename type_of_size< alignment_types, alignment_of< to_align >::value >::type

template< typename T >
struct alignment_of;

template< typename T >
struct alignment_of_hack
{
    char c;
    T t;
    alignment_of_hack();
};

template< size_t A, size_t S >
struct alignment_logic
{
    enum { value = A < S ? A : S };
};

template< typename T >
struct alignment_of
{
    enum { value = alignment_logic<
        sizeof( alignment_of_hack<T> ) - sizeof(T), sizeof(T) >::value };
};

template< typename List, size_t N >
struct type_of_size
{
    typedef typename std11::conditional<
        N == sizeof( typename List::head ),
            typename List::head,
            typename type_of_size<typename List::tail, N >::type >::type type;
};

template< size_t N >
struct type_of_size< nulltype, N >
{
    typedef optional_CONFIG_ALIGN_AS_FALLBACK type;
};

template< typename T>
struct struct_t { T _; };

#define optional_ALIGN_TYPE( type ) \
    typelist< type , typelist< struct_t< type >

struct Unknown;

typedef
    optional_ALIGN_TYPE( char ),
    optional_ALIGN_TYPE( short ),
    optional_ALIGN_TYPE( int ),
    optional_ALIGN_TYPE( long ),
    optional_ALIGN_TYPE( float ),
    optional_ALIGN_TYPE( double ),
    optional_ALIGN_TYPE( long double ),

    optional_ALIGN_TYPE( char *),
    optional_ALIGN_TYPE( short * ),
    optional_ALIGN_TYPE( int * ),
    optional_ALIGN_TYPE( long * ),
    optional_ALIGN_TYPE( float * ),
    optional_ALIGN_TYPE( double * ),
    optional_ALIGN_TYPE( long double * ),

    optional_ALIGN_TYPE( Unknown ( * )( Unknown ) ),
    optional_ALIGN_TYPE( Unknown * Unknown::*     ),
    optional_ALIGN_TYPE( Unknown ( Unknown::* )( Unknown ) ),

    nulltype
    > > > > > > >    > > > > > > >
    > > > > > > >    > > > > > > >
    > > > > > >
    alignment_types;

#undef optional_ALIGN_TYPE

#endif // optional_CONFIG_MAX_ALIGN_HACK

/// C++03 constructed union to hold value.

template< typename T >
union storage_t
{
//private:
//    template< typename > friend class optional;

    typedef T value_type;

    storage_t() optional_is_default

    explicit storage_t( value_type const & v )
    {
        construct_value( v );
    }

    void construct_value( value_type const & v )
    {
        ::new( value_ptr() ) value_type( v );
    }

#if optional_CPP11_OR_GREATER

    explicit storage_t( value_type && v )
    {
        construct_value( std::move( v ) );
    }

    void construct_value( value_type && v )
    {
        ::new( value_ptr() ) value_type( std::move( v ) );
    }

    template< class... Args >
    storage_t( nonstd_lite_in_place_t(T), Args&&... args )
    {
        emplace( std::forward<Args>(args)... );
    }

    template< class... Args >
    void emplace( Args&&... args )
    {
        ::new( value_ptr() ) value_type( std::forward<Args>(args)... );
    }

    template< class U, class... Args >
    void emplace( std::initializer_list<U> il, Args&&... args )
    {
        ::new( value_ptr() ) value_type( il, std::forward<Args>(args)... );
    }

#endif

    void destruct_value()
    {
        value_ptr()->~T();
    }

    optional_nodiscard value_type const * value_ptr() const
    {
        return as<value_type>();
    }

    value_type * value_ptr()
    {
        return as<value_type>();
    }

    optional_nodiscard value_type const & value() const optional_ref_qual
    {
        return * value_ptr();
    }

    value_type & value() optional_ref_qual
    {
        return * value_ptr();
    }

#if optional_HAVE( REF_QUALIFIER )

    optional_nodiscard value_type const && value() const optional_refref_qual
    {
        return std::move( value() );
    }

    value_type && value() optional_refref_qual
    {
        return std::move( value() );
    }

#endif

#if optional_CPP11_OR_GREATER

    using aligned_storage_t = typename std::aligned_storage< sizeof(value_type), alignof(value_type) >::type;
    aligned_storage_t data;

#elif optional_CONFIG_MAX_ALIGN_HACK

    typedef struct { unsigned char data[ sizeof(value_type) ]; } aligned_storage_t;

    max_align_t hack;
    aligned_storage_t data;

#else
    typedef optional_ALIGN_AS(value_type) align_as_type;

    typedef struct { align_as_type data[ 1 + ( sizeof(value_type) - 1 ) / sizeof(align_as_type) ]; } aligned_storage_t;
    aligned_storage_t data;

#   undef optional_ALIGN_AS

#endif // optional_CONFIG_MAX_ALIGN_HACK

    optional_nodiscard void * ptr() optional_noexcept
    {
        return &data;
    }

    optional_nodiscard void const * ptr() const optional_noexcept
    {
        return &data;
    }

    template <typename U>
    optional_nodiscard U * as()
    {
        return reinterpret_cast<U*>( ptr() );
    }

    template <typename U>
    optional_nodiscard U const * as() const
    {
        return reinterpret_cast<U const *>( ptr() );
    }
};

} // namespace detail

/// disengaged state tag

struct nullopt_t
{
    struct init{};
    explicit optional_constexpr nullopt_t( init /*unused*/ ) optional_noexcept {}
};

#if optional_HAVE( CONSTEXPR_11 )
constexpr nullopt_t nullopt{ nullopt_t::init{} };
#else
// extra parenthesis to prevent the most vexing parse:
const nullopt_t nullopt(( nullopt_t::init() ));
#endif

/// optional access error

#if ! optional_CONFIG_NO_EXCEPTIONS

class bad_optional_access : public std::logic_error
{
public:
  explicit bad_optional_access()
  : logic_error( "bad optional access" ) {}
};

#endif //optional_CONFIG_NO_EXCEPTIONS

/// optional

template< typename T>
class optional
{
    optional_static_assert(( !std::is_same<typename std::remove_cv<T>::type, nullopt_t>::value  ),
        "T in optional<T> must not be of type 'nullopt_t'.")

    optional_static_assert(( !std::is_same<typename std::remove_cv<T>::type, in_place_t>::value ),
        "T in optional<T> must not be of type 'in_place_t'.")

    optional_static_assert(( std::is_object<T>::value && std::is_destructible<T>::value && !std::is_array<T>::value ),
        "T in optional<T> must meet the Cpp17Destructible requirements.")

private:
    template< typename > friend class optional;

    typedef void (optional::*safe_bool)() const;

public:
    typedef T value_type;

     // x.x.3.1, constructors

    // 1a - default construct
    optional_constexpr optional() optional_noexcept
    : has_value_( false )
    , contained()
    {}

    // 1b - construct explicitly empty
    // NOLINTNEXTLINE( google-explicit-constructor, hicpp-explicit-conversions )
    optional_constexpr optional( nullopt_t /*unused*/ ) optional_noexcept
    : has_value_( false )
    , contained()
    {}

    // 2 - copy-construct
#if optional_CPP11_OR_GREATER
    // template< typename U = T
    //     optional_REQUIRES_T(
    //         std::is_copy_constructible<U>::value
    //         || std11::is_trivially_copy_constructible<U>::value
    //     )
    // >
#endif
    optional_constexpr14 optional( optional const & other )
    : has_value_( other.has_value() )
    {
        if ( other.has_value() )
        {
            contained.construct_value( other.contained.value() );
        }
    }

#if optional_CPP11_OR_GREATER

    // 3 (C++11) - move-construct from optional
    template< typename U = T
        optional_REQUIRES_T(
            std11::is_move_constructible<U>::value
            || std11::is_trivially_move_constructible<U>::value
        )
    >
    optional_constexpr14 optional( optional && other )
    // NOLINTNEXTLINE( performance-noexcept-move-constructor )
        noexcept( std11::is_nothrow_move_constructible<T>::value )
    : has_value_( other.has_value() )
    {
        if ( other.has_value() )
        {
            contained.construct_value( std::move( other.contained.value() ) );
        }
    }

    // 4a (C++11) - explicit converting copy-construct from optional
    template< typename U
        optional_REQUIRES_T(
            std::is_constructible<T, U const &>::value
            && !std::is_constructible<T, optional<U> &          >::value
            && !std::is_constructible<T, optional<U> &&         >::value
            && !std::is_constructible<T, optional<U> const &    >::value
            && !std::is_constructible<T, optional<U> const &&   >::value
            && !std::is_convertible<     optional<U> &       , T>::value
            && !std::is_convertible<     optional<U> &&      , T>::value
            && !std::is_convertible<     optional<U> const & , T>::value
            && !std::is_convertible<     optional<U> const &&, T>::value
            && !std::is_convertible<               U const & , T>::value /*=> explicit */
        )
    >
    explicit optional( optional<U> const & other )
    : has_value_( other.has_value() )
    {
        if ( other.has_value() )
        {
            contained.construct_value( T{ other.contained.value() } );
        }
    }
#endif // optional_CPP11_OR_GREATER

    // 4b (C++98 and later) - non-explicit converting copy-construct from optional
    template< typename U
#if optional_CPP11_OR_GREATER
        optional_REQUIRES_T(
            std::is_constructible<T, U const &>::value
            && !std::is_constructible<T, optional<U> &          >::value
            && !std::is_constructible<T, optional<U> &&         >::value
            && !std::is_constructible<T, optional<U> const &    >::value
            && !std::is_constructible<T, optional<U> const &&   >::value
            && !std::is_convertible<     optional<U> &       , T>::value
            && !std::is_convertible<     optional<U> &&      , T>::value
            && !std::is_convertible<     optional<U> const & , T>::value
            && !std::is_convertible<     optional<U> const &&, T>::value
            &&  std::is_convertible<               U const & , T>::value /*=> non-explicit */
        )
#endif // optional_CPP11_OR_GREATER
    >
    // NOLINTNEXTLINE( google-explicit-constructor, hicpp-explicit-conversions )
    /*non-explicit*/ optional( optional<U> const & other )
    : has_value_( other.has_value() )
    {
        if ( other.has_value() )
        {
            contained.construct_value( other.contained.value() );
        }
    }

#if optional_CPP11_OR_GREATER

    // 5a (C++11) - explicit converting move-construct from optional
    template< typename U
        optional_REQUIRES_T(
            std::is_constructible<T, U &&>::value
            && !std::is_constructible<T, optional<U> &          >::value
            && !std::is_constructible<T, optional<U> &&         >::value
            && !std::is_constructible<T, optional<U> const &    >::value
            && !std::is_constructible<T, optional<U> const &&   >::value
            && !std::is_convertible<     optional<U> &       , T>::value
            && !std::is_convertible<     optional<U> &&      , T>::value
            && !std::is_convertible<     optional<U> const & , T>::value
            && !std::is_convertible<     optional<U> const &&, T>::value
            && !std::is_convertible<                     U &&, T>::value /*=> explicit */
        )
    >
    explicit optional( optional<U> && other
    )
    : has_value_( other.has_value() )
    {
        if ( other.has_value() )
        {
            contained.construct_value( T{ std::move( other.contained.value() ) } );
        }
    }

    // 5a (C++11) - non-explicit converting move-construct from optional
    template< typename U
        optional_REQUIRES_T(
            std::is_constructible<T, U &&>::value
            && !std::is_constructible<T, optional<U> &          >::value
            && !std::is_constructible<T, optional<U> &&         >::value
            && !std::is_constructible<T, optional<U> const &    >::value
            && !std::is_constructible<T, optional<U> const &&   >::value
            && !std::is_convertible<     optional<U> &       , T>::value
            && !std::is_convertible<     optional<U> &&      , T>::value
            && !std::is_convertible<     optional<U> const & , T>::value
            && !std::is_convertible<     optional<U> const &&, T>::value
            &&  std::is_convertible<                     U &&, T>::value /*=> non-explicit */
        )
    >
    // NOLINTNEXTLINE( google-explicit-constructor, hicpp-explicit-conversions )
    /*non-explicit*/ optional( optional<U> && other )
    : has_value_( other.has_value() )
    {
        if ( other.has_value() )
        {
            contained.construct_value( std::move( other.contained.value() ) );
        }
    }

    // 6 (C++11) - in-place construct
    template< typename... Args
        optional_REQUIRES_T(
            std::is_constructible<T, Args&&...>::value
        )
    >
    optional_constexpr explicit optional( nonstd_lite_in_place_t(T), Args&&... args )
    : has_value_( true )
    , contained( in_place, std::forward<Args>(args)... )
    {}

    // 7 (C++11) - in-place construct,  initializer-list
    template< typename U, typename... Args
        optional_REQUIRES_T(
            std::is_constructible<T, std::initializer_list<U>&, Args&&...>::value
        )
    >
    optional_constexpr explicit optional( nonstd_lite_in_place_t(T), std::initializer_list<U> il, Args&&... args )
    : has_value_( true )
    , contained( T( il, std::forward<Args>(args)...) )
    {}

    // 8a (C++11) - explicit move construct from value
    template< typename U = T
        optional_REQUIRES_T(
            std::is_constructible<T, U&&>::value
            && !std::is_same<typename std20::remove_cvref<U>::type, nonstd_lite_in_place_t(U)>::value
            && !std::is_same<typename std20::remove_cvref<U>::type, optional<T>>::value
            && !std::is_convertible<U&&, T>::value /*=> explicit */
        )
    >
    optional_constexpr explicit optional( U && value )
    : has_value_( true )
    , contained( nonstd_lite_in_place(T), std::forward<U>( value ) )
    {}

    // 8b (C++11) - non-explicit move construct from value
    template< typename U = T
        optional_REQUIRES_T(
            std::is_constructible<T, U&&>::value
            && !std::is_same<typename std20::remove_cvref<U>::type, nonstd_lite_in_place_t(U)>::value
            && !std::is_same<typename std20::remove_cvref<U>::type, optional<T>>::value
            && std::is_convertible<U&&, T>::value /*=> non-explicit */
        )
    >
    // NOLINTNEXTLINE( google-explicit-constructor, hicpp-explicit-conversions )
    optional_constexpr /*non-explicit*/ optional( U && value )
    : has_value_( true )
    , contained( nonstd_lite_in_place(T), std::forward<U>( value ) )
    {}

#else // optional_CPP11_OR_GREATER

    // 8 (C++98)
    optional( value_type const & value )
    : has_value_( true )
    , contained( value )
    {}

#endif // optional_CPP11_OR_GREATER

    // x.x.3.2, destructor

    ~optional()
    {
        if ( has_value() )
        {
            contained.destruct_value();
        }
    }

    // x.x.3.3, assignment

    // 1 (C++98and later) -  assign explicitly empty
    optional & operator=( nullopt_t /*unused*/) optional_noexcept
    {
        reset();
        return *this;
    }

    // 2 (C++98and later) - copy-assign from optional
#if optional_CPP11_OR_GREATER
    // NOLINTNEXTLINE( cppcoreguidelines-c-copy-assignment-signature, misc-unconventional-assign-operator )
    optional_REQUIRES_R(
        optional &,
        true
//      std::is_copy_constructible<T>::value
//      && std::is_copy_assignable<T>::value
    )
    operator=( optional const & other )
        noexcept(
            std11::is_nothrow_move_assignable<T>::value
            && std11::is_nothrow_move_constructible<T>::value
        )
#else
    optional & operator=( optional const & other )
#endif
    {
        if      ( (has_value() == true ) && (other.has_value() == false) ) { reset(); }
        else if ( (has_value() == false) && (other.has_value() == true ) ) { initialize( *other ); }
        else if ( (has_value() == true ) && (other.has_value() == true ) ) { contained.value() = *other; }
        return *this;
    }

#if optional_CPP11_OR_GREATER

    // 3 (C++11) - move-assign from optional
    // NOLINTNEXTLINE( cppcoreguidelines-c-copy-assignment-signature, misc-unconventional-assign-operator )
    optional_REQUIRES_R(
        optional &,
        true
//      std11::is_move_constructible<T>::value
//      && std::is_move_assignable<T>::value
    )
    operator=( optional && other ) noexcept
    {
        if      ( (has_value() == true ) && (other.has_value() == false) ) { reset(); }
        else if ( (has_value() == false) && (other.has_value() == true ) ) { initialize( std::move( *other ) ); }
        else if ( (has_value() == true ) && (other.has_value() == true ) ) { contained.value() = std::move( *other ); }
        return *this;
    }

    // 4 (C++11) - move-assign from value
    template< typename U = T >
        // NOLINTNEXTLINE( cppcoreguidelines-c-copy-assignment-signature, misc-unconventional-assign-operator )
        optional_REQUIRES_R(
            optional &,
            std::is_constructible<T , U>::value
            && std11::is_assignable<T&, U>::value
            && !std::is_same<typename std20::remove_cvref<U>::type, nonstd_lite_in_place_t(U)>::value
            && !std::is_same<typename std20::remove_cvref<U>::type, optional<T>>::value
            && !(std::is_scalar<T>::value && std::is_same<T, typename std::decay<U>::type>::value)
        )
    operator=( U && value )
    {
        if ( has_value() )
        {
            contained.value() = std::forward<U>( value );
        }
        else
        {
            initialize( T( std::forward<U>( value ) ) );
        }
        return *this;
    }

#else // optional_CPP11_OR_GREATER

    // 4 (C++98) - copy-assign from value
    template< typename U /*= T*/ >
    optional & operator=( U const & value )
    {
        if ( has_value() ) contained.value() = value;
        else               initialize( T( value ) );
        return *this;
    }

#endif // optional_CPP11_OR_GREATER

    // 5 (C++98 and later) - converting copy-assign from optional
    template< typename U >
#if optional_CPP11_OR_GREATER
        // NOLINTNEXTLINE( cppcoreguidelines-c-copy-assignment-signature, misc-unconventional-assign-operator )
        optional_REQUIRES_R(
            optional&,
            std::is_constructible<  T , U const &>::value
            &&  std11::is_assignable< T&, U const &>::value
            && !std::is_constructible<T, optional<U> &          >::value
            && !std::is_constructible<T, optional<U> &&         >::value
            && !std::is_constructible<T, optional<U> const &    >::value
            && !std::is_constructible<T, optional<U> const &&   >::value
            && !std::is_convertible<     optional<U> &       , T>::value
            && !std::is_convertible<     optional<U> &&      , T>::value
            && !std::is_convertible<     optional<U> const & , T>::value
            && !std::is_convertible<     optional<U> const &&, T>::value
            && !std11::is_assignable<  T&, optional<U> &          >::value
            && !std11::is_assignable<  T&, optional<U> &&         >::value
            && !std11::is_assignable<  T&, optional<U> const &    >::value
            && !std11::is_assignable<  T&, optional<U> const &&   >::value
        )
#else
    optional&
#endif // optional_CPP11_OR_GREATER
    operator=( optional<U> const & other )
    {
        return *this = optional( other );
    }

#if optional_CPP11_OR_GREATER

    // 6 (C++11) -  converting move-assign from optional
    template< typename U >
        // NOLINTNEXTLINE( cppcoreguidelines-c-copy-assignment-signature, misc-unconventional-assign-operator )
        optional_REQUIRES_R(
            optional&,
            std::is_constructible<  T , U>::value
            &&  std11::is_assignable< T&, U>::value
            && !std::is_constructible<T, optional<U> &          >::value
            && !std::is_constructible<T, optional<U> &&         >::value
            && !std::is_constructible<T, optional<U> const &    >::value
            && !std::is_constructible<T, optional<U> const &&   >::value
            && !std::is_convertible<     optional<U> &       , T>::value
            && !std::is_convertible<     optional<U> &&      , T>::value
            && !std::is_convertible<     optional<U> const & , T>::value
            && !std::is_convertible<     optional<U> const &&, T>::value
            && !std11::is_assignable<  T&, optional<U> &          >::value
            && !std11::is_assignable<  T&, optional<U> &&         >::value
            && !std11::is_assignable<  T&, optional<U> const &    >::value
            && !std11::is_assignable<  T&, optional<U> const &&   >::value
        )
    operator=( optional<U> && other )
    {
        return *this = optional( std::move( other ) );
    }

    // 7 (C++11) - emplace
    template< typename... Args
        optional_REQUIRES_T(
            std::is_constructible<T, Args&&...>::value
        )
    >
    T& emplace( Args&&... args )
    {
        *this = nullopt;
        contained.emplace( std::forward<Args>(args)...  );
        has_value_ = true;
        return contained.value();
    }

    // 8 (C++11) - emplace, initializer-list
    template< typename U, typename... Args
        optional_REQUIRES_T(
            std::is_constructible<T, std::initializer_list<U>&, Args&&...>::value
        )
    >
    T& emplace( std::initializer_list<U> il, Args&&... args )
    {
        *this = nullopt;
        contained.emplace( il, std::forward<Args>(args)...  );
        has_value_ = true;
        return contained.value();
    }

#endif // optional_CPP11_OR_GREATER

    // x.x.3.4, swap

    void swap( optional & other )
#if optional_CPP11_OR_GREATER
        noexcept(
            std11::is_nothrow_move_constructible<T>::value
            && std17::is_nothrow_swappable<T>::value
        )
#endif
    {
        using std::swap;
        if      ( (has_value() == true ) && (other.has_value() == true ) ) { swap( **this, *other ); }
        else if ( (has_value() == false) && (other.has_value() == true ) ) { initialize( std11::move(*other) ); other.reset(); }
        else if ( (has_value() == true ) && (other.has_value() == false) ) { other.initialize( std11::move(**this) ); reset(); }
    }

    // x.x.3.5, observers

    optional_constexpr value_type const * operator ->() const
    {
        return assert( has_value() ),
            contained.value_ptr();
    }

    optional_constexpr14 value_type * operator ->()
    {
        return assert( has_value() ),
            contained.value_ptr();
    }

    optional_constexpr value_type const & operator *() const optional_ref_qual
    {
        return assert( has_value() ),
            contained.value();
    }

    optional_constexpr14 value_type & operator *() optional_ref_qual
    {
        return assert( has_value() ),
            contained.value();
    }

#if optional_HAVE( REF_QUALIFIER )

    optional_constexpr value_type const && operator *() const optional_refref_qual
    {
        return std::move( **this );
    }

    optional_constexpr14 value_type && operator *() optional_refref_qual
    {
        return std::move( **this );
    }

#endif

#if optional_CPP11_OR_GREATER
    optional_constexpr explicit operator bool() const optional_noexcept
    {
        return has_value();
    }
#else
    optional_constexpr operator safe_bool() const optional_noexcept
    {
        return has_value() ? &optional::this_type_does_not_support_comparisons : 0;
    }
#endif

    // NOLINTNEXTLINE( modernize-use-nodiscard )
    /*optional_nodiscard*/ optional_constexpr bool has_value() const optional_noexcept
    {
        return has_value_;
    }

    // NOLINTNEXTLINE( modernize-use-nodiscard )
    /*optional_nodiscard*/ optional_constexpr14 value_type const & value() const optional_ref_qual
    {
#if optional_CONFIG_NO_EXCEPTIONS
        assert( has_value() );
#else
        if ( ! has_value() )
        {
            throw bad_optional_access();
        }
#endif
        return contained.value();
    }

    optional_constexpr14 value_type & value() optional_ref_qual
    {
#if optional_CONFIG_NO_EXCEPTIONS
        assert( has_value() );
#else
        if ( ! has_value() )
        {
            throw bad_optional_access();
        }
#endif
        return contained.value();
    }

#if optional_HAVE( REF_QUALIFIER )  &&  ( !optional_COMPILER_GNUC_VERSION || optional_COMPILER_GNUC_VERSION >= 490 )

    // NOLINTNEXTLINE( modernize-use-nodiscard )
    /*optional_nodiscard*/ optional_constexpr value_type const && value() const optional_refref_qual
    {
        return std::move( value() );
    }

    optional_constexpr14 value_type && value() optional_refref_qual
    {
        return std::move( value() );
    }

#endif

#if optional_HAVE( REF_QUALIFIER )

    template< typename U >
    optional_constexpr value_type value_or( U && v ) const optional_ref_qual
    {
        return has_value() ? contained.value() : static_cast<T>(std::forward<U>( v ) );
    }

    template< typename U >
    optional_constexpr14 value_type value_or( U && v ) optional_refref_qual
    {
#if optional_COMPILER_CLANG_VERSION
        return has_value() ? /*std::move*/( contained.value() ) : static_cast<T>(std::forward<U>( v ) );
#else
        return has_value() ? std::move( contained.value() ) : static_cast<T>(std::forward<U>( v ) );
#endif
    }

#else

    template< typename U >
    optional_constexpr value_type value_or( U const & v ) const
    {
        return has_value() ? contained.value() : static_cast<value_type>( v );
    }

#endif // optional_HAVE( REF_QUALIFIER )

#if !optional_CONFIG_NO_EXTENSIONS
#if  optional_HAVE( REF_QUALIFIER )

    template< typename F >
    optional_constexpr value_type value_or_eval( F f ) const &
    {
        return has_value() ? contained.value() : f();
    }

    template< typename F >
    optional_constexpr14 value_type value_or_eval( F f ) &&
    {
        if ( has_value() )
        {
            return std::move( contained.value() );
        }
        else
        {
            return f();
        }
    }

#else

    template< typename F >
    optional_constexpr value_type value_or_eval( F f ) const
    {
        return has_value() ? contained.value() : f();
    }

#endif //  optional_HAVE( REF_QUALIFIER )
#endif // !optional_CONFIG_NO_EXTENSIONS

    // x.x.3.6, modifiers

    void reset() optional_noexcept
    {
        if ( has_value() )
        {
            contained.destruct_value();
        }

        has_value_ = false;
    }

private:
    void this_type_does_not_support_comparisons() const {}

    template< typename V >
    void initialize( V const & value )
    {
        assert( ! has_value()  );
        contained.construct_value( value );
        has_value_ = true;
    }

#if optional_CPP11_OR_GREATER
    template< typename V >
    void initialize( V && value )
    {
        assert( ! has_value()  );
        contained.construct_value( std::move( value ) );
        has_value_ = true;
    }

#endif

private:
    bool has_value_;
    detail::storage_t< value_type > contained;

};

// Relational operators

template< typename T, typename U >
optional_nodiscard optional_constexpr bool operator==( optional<T> const & x, optional<U> const & y )
{
    return bool(x) != bool(y) ? false : !bool( x ) ? true : *x == *y;
}

template< typename T, typename U >
optional_nodiscard optional_constexpr bool operator!=( optional<T> const & x, optional<U> const & y )
{
    return !(x == y);
}

template< typename T, typename U >
optional_nodiscard optional_constexpr bool operator<( optional<T> const & x, optional<U> const & y )
{
    return (!y) ? false : (!x) ? true : *x < *y;
}

template< typename T, typename U >
optional_nodiscard optional_constexpr bool operator>( optional<T> const & x, optional<U> const & y )
{
    return (y < x);
}

template< typename T, typename U >
optional_nodiscard optional_constexpr bool operator<=( optional<T> const & x, optional<U> const & y )
{
    return !(y < x);
}

template< typename T, typename U >
optional_nodiscard optional_constexpr bool operator>=( optional<T> const & x, optional<U> const & y )
{
    return !(x < y);
}

// Comparison with nullopt

template< typename T >
optional_nodiscard optional_constexpr bool operator==( optional<T> const & x, nullopt_t /*unused*/ ) optional_noexcept
{
    return (!x);
}

template< typename T >
optional_nodiscard optional_constexpr bool operator==( nullopt_t /*unused*/, optional<T> const & x ) optional_noexcept
{
    return (!x);
}

template< typename T >
optional_nodiscard optional_constexpr bool operator!=( optional<T> const & x, nullopt_t /*unused*/ ) optional_noexcept
{
    return bool(x);
}

template< typename T >
optional_nodiscard optional_constexpr bool operator!=( nullopt_t /*unused*/, optional<T> const & x ) optional_noexcept
{
    return bool(x);
}

template< typename T >
optional_nodiscard optional_constexpr bool operator<( optional<T> const & /*unused*/, nullopt_t /*unused*/ ) optional_noexcept
{
    return false;
}

template< typename T >
optional_nodiscard optional_constexpr bool operator<( nullopt_t /*unused*/, optional<T> const & x ) optional_noexcept
{
    return bool(x);
}

template< typename T >
optional_nodiscard optional_constexpr bool operator<=( optional<T> const & x, nullopt_t /*unused*/ ) optional_noexcept
{
    return (!x);
}

template< typename T >
optional_nodiscard optional_constexpr bool operator<=( nullopt_t /*unused*/, optional<T> const & /*unused*/ ) optional_noexcept
{
    return true;
}

template< typename T >
optional_nodiscard optional_constexpr bool operator>( optional<T> const & x, nullopt_t /*unused*/ ) optional_noexcept
{
    return bool(x);
}

template< typename T >
optional_nodiscard optional_constexpr bool operator>( nullopt_t /*unused*/, optional<T> const & /*unused*/ ) optional_noexcept
{
    return false;
}

template< typename T >
optional_nodiscard optional_constexpr bool operator>=( optional<T> const & /*unused*/, nullopt_t /*unused*/ ) optional_noexcept
{
    return true;
}

template< typename T >
optional_nodiscard optional_constexpr bool operator>=( nullopt_t /*unused*/, optional<T> const & x ) optional_noexcept
{
    return (!x);
}

// Comparison with T

template< typename T, typename U >
optional_nodiscard optional_constexpr bool operator==( optional<T> const & x, U const & v )
{
    return bool(x) ? *x == v : false;
}

template< typename T, typename U >
optional_nodiscard optional_constexpr bool operator==( U const & v, optional<T> const & x )
{
    return bool(x) ? v == *x : false;
}

template< typename T, typename U >
optional_nodiscard optional_constexpr bool operator!=( optional<T> const & x, U const & v )
{
    return bool(x) ? *x != v : true;
}

template< typename T, typename U >
optional_nodiscard optional_constexpr bool operator!=( U const & v, optional<T> const & x )
{
    return bool(x) ? v != *x : true;
}

template< typename T, typename U >
optional_nodiscard optional_constexpr bool operator<( optional<T> const & x, U const & v )
{
    return bool(x) ? *x < v : true;
}

template< typename T, typename U >
optional_nodiscard optional_constexpr bool operator<( U const & v, optional<T> const & x )
{
    return bool(x) ? v < *x : false;
}

template< typename T, typename U >
optional_nodiscard optional_constexpr bool operator<=( optional<T> const & x, U const & v )
{
    return bool(x) ? *x <= v : true;
}

template< typename T, typename U >
optional_nodiscard optional_constexpr bool operator<=( U const & v, optional<T> const & x )
{
    return bool(x) ? v <= *x : false;
}

template< typename T, typename U >
optional_nodiscard optional_constexpr bool operator>( optional<T> const & x, U const & v )
{
    return bool(x) ? *x > v : false;
}

template< typename T, typename U >
optional_nodiscard optional_constexpr bool operator>( U const & v, optional<T> const & x )
{
    return bool(x) ? v > *x : true;
}

template< typename T, typename U >
optional_nodiscard optional_constexpr bool operator>=( optional<T> const & x, U const & v )
{
    return bool(x) ? *x >= v : false;
}

template< typename T, typename U >
optional_nodiscard optional_constexpr bool operator>=( U const & v, optional<T> const & x )
{
    return bool(x) ? v >= *x : true;
}

// Specialized algorithms

template< typename T
#if optional_CPP11_OR_GREATER
    optional_REQUIRES_T(
        std11::is_move_constructible<T>::value
        && std17::is_swappable<T>::value )
#endif
>
void swap( optional<T> & x, optional<T> & y )
#if optional_CPP11_OR_GREATER
    noexcept( noexcept( x.swap(y) ) )
#endif
{
    x.swap( y );
}

#if optional_CPP11_OR_GREATER

template< typename T >
optional_constexpr optional< typename std::decay<T>::type > make_optional( T && value )
{
    return optional< typename std::decay<T>::type >( std::forward<T>( value ) );
}

template< typename T, typename...Args >
optional_constexpr optional<T> make_optional( Args&&... args )
{
    return optional<T>( nonstd_lite_in_place(T), std::forward<Args>(args)...);
}

template< typename T, typename U, typename... Args >
optional_constexpr optional<T> make_optional( std::initializer_list<U> il, Args&&... args )
{
    return optional<T>( nonstd_lite_in_place(T), il, std::forward<Args>(args)...);
}

#else

template< typename T >
optional<T> make_optional( T const & value )
{
    return optional<T>( value );
}

#endif // optional_CPP11_OR_GREATER

} // namespace optional_lite

using optional_lite::optional;
using optional_lite::nullopt_t;
using optional_lite::nullopt;

#if ! optional_CONFIG_NO_EXCEPTIONS
using optional_lite::bad_optional_access;
#endif

using optional_lite::make_optional;

} // namespace nonstd

#if optional_CPP11_OR_GREATER

// specialize the std::hash algorithm:

namespace std {

template< class T >
struct hash< nonstd::optional<T> >
{
public:
    std::size_t operator()( nonstd::optional<T> const & v ) const optional_noexcept
    {
        return bool( v ) ? std::hash<T>{}( *v ) : 0;
    }
};

} //namespace std

#endif // optional_CPP11_OR_GREATER

#if defined(__clang__)
# pragma clang diagnostic pop
#elif defined(__GNUC__)
# pragma GCC   diagnostic pop
#elif defined(_MSC_VER )
# pragma warning( pop )
#endif

#endif // optional_USES_STD_OPTIONAL

#endif // NONSTD_OPTIONAL_LITE_HPP