summaryrefslogtreecommitdiffstats
blob: f1a83fca0337b4d130834fcae15e823dcf6da7a9 (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
///////////////////////////////////////////////////////////////////////////////
/// \file traits.hpp
/// Contains definitions for child\<\>, child_c\<\>, left\<\>,
/// right\<\>, tag_of\<\>, and the helper functions child(), child_c(),
/// value(), left() and right().
//
//  Copyright 2008 Eric Niebler. Distributed under the Boost
//  Software License, Version 1.0. (See accompanying file
//  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

#ifndef BOOST_PROTO_ARG_TRAITS_HPP_EAN_04_01_2005
#define BOOST_PROTO_ARG_TRAITS_HPP_EAN_04_01_2005

#include <boost/config.hpp>
#include <boost/detail/workaround.hpp>
#include <boost/preprocessor/iteration/iterate.hpp>
#include <boost/preprocessor/repetition/enum.hpp>
#include <boost/preprocessor/repetition/enum_params.hpp>
#include <boost/preprocessor/repetition/enum_trailing_params.hpp>
#include <boost/preprocessor/repetition/repeat.hpp>
#include <boost/preprocessor/repetition/repeat_from_to.hpp>
#include <boost/preprocessor/facilities/intercept.hpp>
#include <boost/preprocessor/arithmetic/sub.hpp>
#include <boost/static_assert.hpp>
#include <boost/mpl/bool.hpp>
#include <boost/proto/detail/template_arity.hpp>
#include <boost/type_traits/is_pod.hpp>
#include <boost/type_traits/is_same.hpp>
#include <boost/type_traits/add_const.hpp>
#include <boost/proto/proto_fwd.hpp>
#include <boost/proto/args.hpp>
#include <boost/proto/domain.hpp>
#include <boost/proto/transform/pass_through.hpp>

#if defined(_MSC_VER)
# pragma warning(push)
# if BOOST_WORKAROUND( BOOST_MSVC, >= 1400 )
#  pragma warning(disable: 4180) // warning C4180: qualifier applied to function type has no meaning; ignored
# endif
# pragma warning(disable : 4714) // function 'xxx' marked as __forceinline not inlined
#endif

namespace boost { namespace proto
{
    namespace detail
    {
        template<typename T, typename Void = void>
        struct if_vararg
        {};

        template<typename T>
        struct if_vararg<T, typename T::proto_is_vararg_>
          : T
        {};

        template<typename T, typename Void = void>
        struct is_callable2_
          : mpl::false_
        {};

        template<typename T>
        struct is_callable2_<T, typename T::proto_is_callable_>
          : mpl::true_
        {};

        template<typename T BOOST_PROTO_TEMPLATE_ARITY_PARAM(long Arity = boost::proto::detail::template_arity<T>::value)>
        struct is_callable_
          : is_callable2_<T>
        {};

    }

    /// \brief Boolean metafunction which detects whether a type is
    /// a callable function object type or not.
    ///
    /// <tt>is_callable\<\></tt> is used by the <tt>when\<\></tt> transform
    /// to determine whether a function type <tt>R(A1,A2,...AN)</tt> is a
    /// callable transform or an object transform. (The former are evaluated
    /// using <tt>call\<\></tt> and the later with <tt>make\<\></tt>.) If
    /// <tt>is_callable\<R\>::value</tt> is \c true, the function type is
    /// a callable transform; otherwise, it is an object transform.
    ///
    /// Unless specialized for a type \c T, <tt>is_callable\<T\>::value</tt>
    /// is computed as follows:
    ///
    /// \li If \c T is a template type <tt>X\<Y0,Y1,...YN\></tt>, where all \c Yx
    /// are types for \c x in <tt>[0,N]</tt>, <tt>is_callable\<T\>::value</tt>
    /// is <tt>is_same\<YN, proto::callable\>::value</tt>.
    /// \li If \c T has a nested type \c proto_is_callable_ that is a typedef
    /// for \c void, <tt>is_callable\<T\>::value</tt> is \c true. (Note: this is
    /// the case for any type that derives from \c proto::callable.)
    /// \li Otherwise, <tt>is_callable\<T\>::value</tt> is \c false.
    template<typename T>
    struct is_callable
      : proto::detail::is_callable_<T>
    {};

    /// INTERNAL ONLY
    ///
    template<>
    struct is_callable<proto::_>
      : mpl::true_
    {};

    /// INTERNAL ONLY
    ///
    template<>
    struct is_callable<proto::callable>
      : mpl::false_
    {};

    /// INTERNAL ONLY
    ///
    template<typename PrimitiveTransform, typename X>
    struct is_callable<proto::transform<PrimitiveTransform, X> >
      : mpl::false_
    {};

    #if BOOST_WORKAROUND(__GNUC__, == 3) || (BOOST_WORKAROUND(__GNUC__, == 4) && __GNUC_MINOR__ == 0)
    // work around GCC bug
    template<typename Tag, typename Args, long N>
    struct is_callable<proto::expr<Tag, Args, N> >
      : mpl::false_
    {};

    // work around GCC bug
    template<typename Tag, typename Args, long N>
    struct is_callable<proto::basic_expr<Tag, Args, N> >
      : mpl::false_
    {};
    #endif

    namespace detail
    {
        template<typename T, typename Void /*= void*/>
        struct is_transform_
          : mpl::false_
        {};

        template<typename T>
        struct is_transform_<T, typename T::proto_is_transform_>
          : mpl::true_
        {};
    }

    /// \brief Boolean metafunction which detects whether a type is
    /// a PrimitiveTransform type or not.
    ///
    /// <tt>is_transform\<\></tt> is used by the <tt>call\<\></tt> transform
    /// to determine whether the function types <tt>R()</tt>, <tt>R(A1)</tt>,
    /// and <tt>R(A1, A2)</tt> should be passed the expression, state and data
    /// parameters (as needed).
    ///
    /// Unless specialized for a type \c T, <tt>is_transform\<T\>::value</tt>
    /// is computed as follows:
    ///
    /// \li If \c T has a nested type \c proto_is_transform_ that is a typedef
    /// for \c void, <tt>is_transform\<T\>::value</tt> is \c true. (Note: this is
    /// the case for any type that derives from an instantiation of \c proto::transform.)
    /// \li Otherwise, <tt>is_transform\<T\>::value</tt> is \c false.
    template<typename T>
    struct is_transform
      : proto::detail::is_transform_<T>
    {};

    namespace detail
    {
        template<typename T, typename Void /*= void*/>
        struct is_aggregate_
          : is_pod<T>
        {};

        template<typename Tag, typename Args, long N>
        struct is_aggregate_<proto::expr<Tag, Args, N>, void>
          : mpl::true_
        {};

        template<typename Tag, typename Args, long N>
        struct is_aggregate_<proto::basic_expr<Tag, Args, N>, void>
          : mpl::true_
        {};

        template<typename T>
        struct is_aggregate_<T, typename T::proto_is_aggregate_>
          : mpl::true_
        {};
    }

    /// \brief A Boolean metafunction that indicates whether a type requires
    /// aggregate initialization.
    ///
    /// <tt>is_aggregate\<\></tt> is used by the <tt>make\<\></tt> transform
    /// to determine how to construct an object of some type \c T, given some
    /// initialization arguments <tt>a0,a1,...aN</tt>.
    /// If <tt>is_aggregate\<T\>::value</tt> is \c true, then an object of
    /// type T will be initialized as <tt>T t = {a0,a1,...aN};</tt>. Otherwise,
    /// it will be initialized as <tt>T t(a0,a1,...aN)</tt>.
    template<typename T>
    struct is_aggregate
      : proto::detail::is_aggregate_<T>
    {};

    /// \brief A Boolean metafunction that indicates whether a given
    /// type \c T is a Proto expression type.
    ///
    /// If \c T has a nested type \c proto_is_expr_ that is a typedef
    /// for \c void, <tt>is_expr\<T\>::value</tt> is \c true. (Note, this
    /// is the case for <tt>proto::expr\<\></tt>, any type that is derived
    /// from <tt>proto::extends\<\></tt> or that uses the
    /// <tt>BOOST_PROTO_BASIC_EXTENDS()</tt> macro.) Otherwise,
    /// <tt>is_expr\<T\>::value</tt> is \c false.
    template<typename T, typename Void /* = void*/>
    struct is_expr
      : mpl::false_
    {};

    /// \brief A Boolean metafunction that indicates whether a given
    /// type \c T is a Proto expression type.
    ///
    /// If \c T has a nested type \c proto_is_expr_ that is a typedef
    /// for \c void, <tt>is_expr\<T\>::value</tt> is \c true. (Note, this
    /// is the case for <tt>proto::expr\<\></tt>, any type that is derived
    /// from <tt>proto::extends\<\></tt> or that uses the
    /// <tt>BOOST_PROTO_BASIC_EXTENDS()</tt> macro.) Otherwise,
    /// <tt>is_expr\<T\>::value</tt> is \c false.
    template<typename T>
    struct is_expr<T, typename T::proto_is_expr_>
      : mpl::true_
    {};
            
    template<typename T>
    struct is_expr<T &, void>
      : is_expr<T>
    {};

    /// \brief A metafunction that returns the tag type of a
    /// Proto expression.
    template<typename Expr>
    struct tag_of
    {
        typedef typename Expr::proto_tag type;
    };

    template<typename Expr>
    struct tag_of<Expr &>
    {
        typedef typename Expr::proto_tag type;
    };

    /// \brief A metafunction that returns the arity of a
    /// Proto expression.
    template<typename Expr>
    struct arity_of
      : Expr::proto_arity
    {};

    template<typename Expr>
    struct arity_of<Expr &>
      : Expr::proto_arity
    {};

    namespace result_of
    {
        /// \brief A metafunction that computes the return type of the \c as_expr()
        /// function.
        template<typename T, typename Domain /*= default_domain*/>
        struct as_expr
        {
            typedef typename Domain::template as_expr<T>::result_type type;
        };

        /// \brief A metafunction that computes the return type of the \c as_child()
        /// function.
        template<typename T, typename Domain /*= default_domain*/>
        struct as_child
        {
            typedef typename Domain::template as_child<T>::result_type type;
        };

        /// \brief A metafunction that returns the type of the Nth child
        /// of a Proto expression, where N is an MPL Integral Constant.
        ///
        /// <tt>result_of::child\<Expr, N\></tt> is equivalent to
        /// <tt>result_of::child_c\<Expr, N::value\></tt>.
        template<typename Expr, typename N /* = mpl::long_<0>*/>
        struct child
          : child_c<Expr, N::value>
        {};

        /// \brief A metafunction that returns the type of the value
        /// of a terminal Proto expression.
        ///
        template<typename Expr>
        struct value
        {
            /// Verify that we are actually operating on a terminal
            BOOST_STATIC_ASSERT(0 == Expr::proto_arity_c);

            /// The raw type of the Nth child as it is stored within
            /// \c Expr. This may be a value or a reference
            typedef typename Expr::proto_child0 value_type;

            /// The "value" type of the child, suitable for storage by value,
            /// computed as follows:
            /// \li <tt>T const(&)[N]</tt> becomes <tt>T[N]</tt>
            /// \li <tt>T[N]</tt> becomes <tt>T[N]</tt>
            /// \li <tt>T(&)[N]</tt> becomes <tt>T[N]</tt>
            /// \li <tt>R(&)(A0,...)</tt> becomes <tt>R(&)(A0,...)</tt>
            /// \li <tt>T const &</tt> becomes <tt>T</tt>
            /// \li <tt>T &</tt> becomes <tt>T</tt>
            /// \li <tt>T</tt> becomes <tt>T</tt>
            typedef typename detail::term_traits<typename Expr::proto_child0>::value_type type;
        };

        template<typename Expr>
        struct value<Expr &>
        {
            /// Verify that we are actually operating on a terminal
            BOOST_STATIC_ASSERT(0 == Expr::proto_arity_c);

            /// The raw type of the Nth child as it is stored within
            /// \c Expr. This may be a value or a reference
            typedef typename Expr::proto_child0 value_type;

            /// The "reference" type of the child, suitable for storage by
            /// reference, computed as follows:
            /// \li <tt>T const(&)[N]</tt> becomes <tt>T const(&)[N]</tt>
            /// \li <tt>T[N]</tt> becomes <tt>T(&)[N]</tt>
            /// \li <tt>T(&)[N]</tt> becomes <tt>T(&)[N]</tt>
            /// \li <tt>R(&)(A0,...)</tt> becomes <tt>R(&)(A0,...)</tt>
            /// \li <tt>T const &</tt> becomes <tt>T const &</tt>
            /// \li <tt>T &</tt> becomes <tt>T &</tt>
            /// \li <tt>T</tt> becomes <tt>T &</tt>
            typedef typename detail::term_traits<typename Expr::proto_child0>::reference type;
        };

        template<typename Expr>
        struct value<Expr const &>
        {
            /// Verify that we are actually operating on a terminal
            BOOST_STATIC_ASSERT(0 == Expr::proto_arity_c);

            /// The raw type of the Nth child as it is stored within
            /// \c Expr. This may be a value or a reference
            typedef typename Expr::proto_child0 value_type;

            /// The "const reference" type of the child, suitable for storage by
            /// const reference, computed as follows:
            /// \li <tt>T const(&)[N]</tt> becomes <tt>T const(&)[N]</tt>
            /// \li <tt>T[N]</tt> becomes <tt>T const(&)[N]</tt>
            /// \li <tt>T(&)[N]</tt> becomes <tt>T(&)[N]</tt>
            /// \li <tt>R(&)(A0,...)</tt> becomes <tt>R(&)(A0,...)</tt>
            /// \li <tt>T const &</tt> becomes <tt>T const &</tt>
            /// \li <tt>T &</tt> becomes <tt>T &</tt>
            /// \li <tt>T</tt> becomes <tt>T const &</tt>
            typedef typename detail::term_traits<typename Expr::proto_child0>::const_reference type;
        };

        /// \brief A metafunction that returns the type of the left child
        /// of a binary Proto expression.
        ///
        /// <tt>result_of::left\<Expr\></tt> is equivalent to
        /// <tt>result_of::child_c\<Expr, 0\></tt>.
        template<typename Expr>
        struct left
          : child_c<Expr, 0>
        {};

        /// \brief A metafunction that returns the type of the right child
        /// of a binary Proto expression.
        ///
        /// <tt>result_of::right\<Expr\></tt> is equivalent to
        /// <tt>result_of::child_c\<Expr, 1\></tt>.
        template<typename Expr>
        struct right
          : child_c<Expr, 1>
        {};

    } // namespace result_of

    /// \brief A metafunction for generating terminal expression types,
    /// a grammar element for matching terminal expressions, and a
    /// PrimitiveTransform that returns the current expression unchanged.
    template<typename T>
    struct terminal
      : proto::transform<terminal<T>, int>
    {
        typedef proto::expr<proto::tag::terminal, term<T>, 0> type;
        typedef proto::basic_expr<proto::tag::terminal, term<T>, 0> proto_grammar;

        template<typename Expr, typename State, typename Data>
        struct impl : transform_impl<Expr, State, Data>
        {
            typedef Expr result_type;

            /// \param e The current expression
            /// \pre <tt>matches\<Expr, terminal\<T\> \>::value</tt> is \c true.
            /// \return \c e
            /// \throw nothrow
            BOOST_FORCEINLINE
            BOOST_PROTO_RETURN_TYPE_STRICT_LOOSE(result_type, typename impl::expr_param)
            operator ()(
                typename impl::expr_param e
              , typename impl::state_param
              , typename impl::data_param
            ) const
            {
                return e;
            }
        };

        /// INTERNAL ONLY
        typedef proto::tag::terminal proto_tag;
        /// INTERNAL ONLY
        typedef T proto_child0;
    };

    /// \brief A metafunction for generating ternary conditional expression types,
    /// a grammar element for matching ternary conditional expressions, and a
    /// PrimitiveTransform that dispatches to the <tt>pass_through\<\></tt>
    /// transform.
    template<typename T, typename U, typename V>
    struct if_else_
      : proto::transform<if_else_<T, U, V>, int>
    {
        typedef proto::expr<proto::tag::if_else_, list3<T, U, V>, 3> type;
        typedef proto::basic_expr<proto::tag::if_else_, list3<T, U, V>, 3> proto_grammar;

        template<typename Expr, typename State, typename Data>
        struct impl
          : detail::pass_through_impl<if_else_, deduce_domain, Expr, State, Data>
        {};

        /// INTERNAL ONLY
        typedef proto::tag::if_else_ proto_tag;
        /// INTERNAL ONLY
        typedef T proto_child0;
        /// INTERNAL ONLY
        typedef U proto_child1;
        /// INTERNAL ONLY
        typedef V proto_child2;
    };

    /// \brief A metafunction for generating nullary expression types with a
    /// specified tag type,
    /// a grammar element for matching nullary expressions, and a
    /// PrimitiveTransform that returns the current expression unchanged.
    ///
    /// Use <tt>nullary_expr\<_, _\></tt> as a grammar element to match any
    /// nullary expression.
    template<typename Tag, typename T>
    struct nullary_expr
      : proto::transform<nullary_expr<Tag, T>, int>
    {
        typedef proto::expr<Tag, term<T>, 0> type;
        typedef proto::basic_expr<Tag, term<T>, 0> proto_grammar;

        template<typename Expr, typename State, typename Data>
        struct impl : transform_impl<Expr, State, Data>
        {
            typedef Expr result_type;

            /// \param e The current expression
            /// \pre <tt>matches\<Expr, nullary_expr\<Tag, T\> \>::value</tt> is \c true.
            /// \return \c e
            /// \throw nothrow
            BOOST_FORCEINLINE
            BOOST_PROTO_RETURN_TYPE_STRICT_LOOSE(result_type, typename impl::expr_param)
            operator ()(
                typename impl::expr_param e
              , typename impl::state_param
              , typename impl::data_param
            ) const
            {
                return e;
            }
        };

        /// INTERNAL ONLY
        typedef Tag proto_tag;
        /// INTERNAL ONLY
        typedef T proto_child0;
    };

    /// \brief A metafunction for generating unary expression types with a
    /// specified tag type,
    /// a grammar element for matching unary expressions, and a
    /// PrimitiveTransform that dispatches to the <tt>pass_through\<\></tt>
    /// transform.
    ///
    /// Use <tt>unary_expr\<_, _\></tt> as a grammar element to match any
    /// unary expression.
    template<typename Tag, typename T>
    struct unary_expr
      : proto::transform<unary_expr<Tag, T>, int>
    {
        typedef proto::expr<Tag, list1<T>, 1> type;
        typedef proto::basic_expr<Tag, list1<T>, 1> proto_grammar;

        template<typename Expr, typename State, typename Data>
        struct impl
          : detail::pass_through_impl<unary_expr, deduce_domain, Expr, State, Data>
        {};

        /// INTERNAL ONLY
        typedef Tag proto_tag;
        /// INTERNAL ONLY
        typedef T proto_child0;
    };

    /// \brief A metafunction for generating binary expression types with a
    /// specified tag type,
    /// a grammar element for matching binary expressions, and a
    /// PrimitiveTransform that dispatches to the <tt>pass_through\<\></tt>
    /// transform.
    ///
    /// Use <tt>binary_expr\<_, _, _\></tt> as a grammar element to match any
    /// binary expression.
    template<typename Tag, typename T, typename U>
    struct binary_expr
      : proto::transform<binary_expr<Tag, T, U>, int>
    {
        typedef proto::expr<Tag, list2<T, U>, 2> type;
        typedef proto::basic_expr<Tag, list2<T, U>, 2> proto_grammar;

        template<typename Expr, typename State, typename Data>
        struct impl
          : detail::pass_through_impl<binary_expr, deduce_domain, Expr, State, Data>
        {};

        /// INTERNAL ONLY
        typedef Tag proto_tag;
        /// INTERNAL ONLY
        typedef T proto_child0;
        /// INTERNAL ONLY
        typedef U proto_child1;
    };

#define BOOST_PROTO_DEFINE_UNARY_METAFUNCTION(Op)                                               \
    template<typename T>                                                                        \
    struct Op                                                                                   \
      : proto::transform<Op<T>, int>                                                            \
    {                                                                                           \
        typedef proto::expr<proto::tag::Op, list1<T>, 1> type;                                  \
        typedef proto::basic_expr<proto::tag::Op, list1<T>, 1> proto_grammar;                   \
                                                                                                \
        template<typename Expr, typename State, typename Data>                                  \
        struct impl                                                                             \
          : detail::pass_through_impl<Op, deduce_domain, Expr, State, Data>                     \
        {};                                                                                     \
                                                                                                \
        typedef proto::tag::Op proto_tag;                                                       \
        typedef T proto_child0;                                                                 \
    };                                                                                          \
    /**/

#define BOOST_PROTO_DEFINE_BINARY_METAFUNCTION(Op)                                              \
    template<typename T, typename U>                                                            \
    struct Op                                                                                   \
      : proto::transform<Op<T, U>, int>                                                         \
    {                                                                                           \
        typedef proto::expr<proto::tag::Op, list2<T, U>, 2> type;                               \
        typedef proto::basic_expr<proto::tag::Op, list2<T, U>, 2> proto_grammar;                \
                                                                                                \
        template<typename Expr, typename State, typename Data>                                  \
        struct impl                                                                             \
          : detail::pass_through_impl<Op, deduce_domain, Expr, State, Data>                     \
        {};                                                                                     \
                                                                                                \
        typedef proto::tag::Op proto_tag;                                                       \
        typedef T proto_child0;                                                                 \
        typedef U proto_child1;                                                                 \
    };                                                                                          \
    /**/

    BOOST_PROTO_DEFINE_UNARY_METAFUNCTION(unary_plus)
    BOOST_PROTO_DEFINE_UNARY_METAFUNCTION(negate)
    BOOST_PROTO_DEFINE_UNARY_METAFUNCTION(dereference)
    BOOST_PROTO_DEFINE_UNARY_METAFUNCTION(complement)
    BOOST_PROTO_DEFINE_UNARY_METAFUNCTION(address_of)
    BOOST_PROTO_DEFINE_UNARY_METAFUNCTION(logical_not)
    BOOST_PROTO_DEFINE_UNARY_METAFUNCTION(pre_inc)
    BOOST_PROTO_DEFINE_UNARY_METAFUNCTION(pre_dec)
    BOOST_PROTO_DEFINE_UNARY_METAFUNCTION(post_inc)
    BOOST_PROTO_DEFINE_UNARY_METAFUNCTION(post_dec)

    BOOST_PROTO_DEFINE_BINARY_METAFUNCTION(shift_left)
    BOOST_PROTO_DEFINE_BINARY_METAFUNCTION(shift_right)
    BOOST_PROTO_DEFINE_BINARY_METAFUNCTION(multiplies)
    BOOST_PROTO_DEFINE_BINARY_METAFUNCTION(divides)
    BOOST_PROTO_DEFINE_BINARY_METAFUNCTION(modulus)
    BOOST_PROTO_DEFINE_BINARY_METAFUNCTION(plus)
    BOOST_PROTO_DEFINE_BINARY_METAFUNCTION(minus)
    BOOST_PROTO_DEFINE_BINARY_METAFUNCTION(less)
    BOOST_PROTO_DEFINE_BINARY_METAFUNCTION(greater)
    BOOST_PROTO_DEFINE_BINARY_METAFUNCTION(less_equal)
    BOOST_PROTO_DEFINE_BINARY_METAFUNCTION(greater_equal)
    BOOST_PROTO_DEFINE_BINARY_METAFUNCTION(equal_to)
    BOOST_PROTO_DEFINE_BINARY_METAFUNCTION(not_equal_to)
    BOOST_PROTO_DEFINE_BINARY_METAFUNCTION(logical_or)
    BOOST_PROTO_DEFINE_BINARY_METAFUNCTION(logical_and)
    BOOST_PROTO_DEFINE_BINARY_METAFUNCTION(bitwise_or)
    BOOST_PROTO_DEFINE_BINARY_METAFUNCTION(bitwise_and)
    BOOST_PROTO_DEFINE_BINARY_METAFUNCTION(bitwise_xor)
    BOOST_PROTO_DEFINE_BINARY_METAFUNCTION(comma)
    BOOST_PROTO_DEFINE_BINARY_METAFUNCTION(mem_ptr)
    BOOST_PROTO_DEFINE_BINARY_METAFUNCTION(assign)
    BOOST_PROTO_DEFINE_BINARY_METAFUNCTION(shift_left_assign)
    BOOST_PROTO_DEFINE_BINARY_METAFUNCTION(shift_right_assign)
    BOOST_PROTO_DEFINE_BINARY_METAFUNCTION(multiplies_assign)
    BOOST_PROTO_DEFINE_BINARY_METAFUNCTION(divides_assign)
    BOOST_PROTO_DEFINE_BINARY_METAFUNCTION(modulus_assign)
    BOOST_PROTO_DEFINE_BINARY_METAFUNCTION(plus_assign)
    BOOST_PROTO_DEFINE_BINARY_METAFUNCTION(minus_assign)
    BOOST_PROTO_DEFINE_BINARY_METAFUNCTION(bitwise_or_assign)
    BOOST_PROTO_DEFINE_BINARY_METAFUNCTION(bitwise_and_assign)
    BOOST_PROTO_DEFINE_BINARY_METAFUNCTION(bitwise_xor_assign)
    BOOST_PROTO_DEFINE_BINARY_METAFUNCTION(subscript)
    BOOST_PROTO_DEFINE_BINARY_METAFUNCTION(member)

    #undef BOOST_PROTO_DEFINE_UNARY_METAFUNCTION
    #undef BOOST_PROTO_DEFINE_BINARY_METAFUNCTION

    #include <boost/proto/detail/traits.hpp>

    namespace functional
    {
        /// \brief A callable PolymorphicFunctionObject that is
        /// equivalent to the \c as_expr() function.
        template<typename Domain   /* = default_domain*/>
        struct as_expr
        {
            BOOST_PROTO_CALLABLE()

            template<typename Sig>
            struct result;

            template<typename This, typename T>
            struct result<This(T)>
            {
                typedef typename Domain::template as_expr<T>::result_type type;
            };

            template<typename This, typename T>
            struct result<This(T &)>
            {
                typedef typename Domain::template as_expr<T>::result_type type;
            };

            /// \brief Wrap an object in a Proto terminal if it isn't a
            /// Proto expression already.
            /// \param t The object to wrap.
            /// \return <tt>proto::as_expr\<Domain\>(t)</tt>
            template<typename T>
            BOOST_FORCEINLINE
            typename add_const<typename result<as_expr(T &)>::type>::type
            operator ()(T &t) const
            {
                return typename Domain::template as_expr<T>()(t);
            }

            /// \overload
            ///
            template<typename T>
            BOOST_FORCEINLINE
            typename add_const<typename result<as_expr(T const &)>::type>::type
            operator ()(T const &t) const
            {
                return typename Domain::template as_expr<T const>()(t);
            }

            #if BOOST_WORKAROUND(BOOST_MSVC, == 1310)
            template<typename T, std::size_t N_>
            BOOST_FORCEINLINE
            typename add_const<typename result<as_expr(T (&)[N_])>::type>::type
            operator ()(T (&t)[N_]) const
            {
                return typename Domain::template as_expr<T[N_]>()(t);
            }

            template<typename T, std::size_t N_>
            BOOST_FORCEINLINE
            typename add_const<typename result<as_expr(T const (&)[N_])>::type>::type
            operator ()(T const (&t)[N_]) const
            {
                return typename Domain::template as_expr<T const[N_]>()(t);
            }
            #endif
        };

        /// \brief A callable PolymorphicFunctionObject that is
        /// equivalent to the \c as_child() function.
        template<typename Domain   /* = default_domain*/>
        struct as_child
        {
            BOOST_PROTO_CALLABLE()

            template<typename Sig>
            struct result;

            template<typename This, typename T>
            struct result<This(T)>
            {
                typedef typename Domain::template as_child<T>::result_type type;
            };

            template<typename This, typename T>
            struct result<This(T &)>
            {
                typedef typename Domain::template as_child<T>::result_type type;
            };

            /// \brief Wrap an object in a Proto terminal if it isn't a
            /// Proto expression already.
            /// \param t The object to wrap.
            /// \return <tt>proto::as_child\<Domain\>(t)</tt>
            template<typename T>
            BOOST_FORCEINLINE
            typename add_const<typename result<as_child(T &)>::type>::type
            operator ()(T &t) const
            {
                return typename Domain::template as_child<T>()(t);
            }

            /// \overload
            ///
            template<typename T>
            BOOST_FORCEINLINE
            typename add_const<typename result<as_child(T const &)>::type>::type
            operator ()(T const &t) const
            {
                return typename Domain::template as_child<T const>()(t);
            }
        };

        /// \brief A callable PolymorphicFunctionObject that is
        /// equivalent to the \c child_c() function.
        template<long N>
        struct child_c
        {
            BOOST_PROTO_CALLABLE()

            template<typename Sig>
            struct result;

            template<typename This, typename Expr>
            struct result<This(Expr)>
            {
                typedef typename result_of::child_c<Expr, N>::type type;
            };

            /// \brief Return the Nth child of the given expression.
            /// \param expr The expression node.
            /// \pre <tt>is_expr\<Expr\>::value</tt> is \c true
            /// \pre <tt>N \< Expr::proto_arity::value</tt>
            /// \return <tt>proto::child_c\<N\>(expr)</tt>
            /// \throw nothrow
            template<typename Expr>
            BOOST_FORCEINLINE
            typename result_of::child_c<Expr &, N>::type
            operator ()(Expr &e) const
            {
                return result_of::child_c<Expr &, N>::call(e);
            }

            /// \overload
            ///
            template<typename Expr>
            BOOST_FORCEINLINE
            typename result_of::child_c<Expr const &, N>::type
            operator ()(Expr const &e) const
            {
                return result_of::child_c<Expr const &, N>::call(e);
            }
        };

        /// \brief A callable PolymorphicFunctionObject that is
        /// equivalent to the \c child() function.
        ///
        /// A callable PolymorphicFunctionObject that is
        /// equivalent to the \c child() function. \c N is required
        /// to be an MPL Integral Constant.
        template<typename N /* = mpl::long_<0>*/>
        struct child
        {
            BOOST_PROTO_CALLABLE()

            template<typename Sig>
            struct result;

            template<typename This, typename Expr>
            struct result<This(Expr)>
            {
                typedef typename result_of::child<Expr, N>::type type;
            };

            /// \brief Return the Nth child of the given expression.
            /// \param expr The expression node.
            /// \pre <tt>is_expr\<Expr\>::value</tt> is \c true
            /// \pre <tt>N::value \< Expr::proto_arity::value</tt>
            /// \return <tt>proto::child\<N\>(expr)</tt>
            /// \throw nothrow
            template<typename Expr>
            BOOST_FORCEINLINE
            typename result_of::child<Expr &, N>::type
            operator ()(Expr &e) const
            {
                return result_of::child<Expr &, N>::call(e);
            }

            /// \overload
            ///
            template<typename Expr>
            BOOST_FORCEINLINE
            typename result_of::child<Expr const &, N>::type
            operator ()(Expr const &e) const
            {
                return result_of::child<Expr const &, N>::call(e);
            }
        };

        /// \brief A callable PolymorphicFunctionObject that is
        /// equivalent to the \c value() function.
        struct value
        {
            BOOST_PROTO_CALLABLE()

            template<typename Sig>
            struct result;

            template<typename This, typename Expr>
            struct result<This(Expr)>
            {
                typedef typename result_of::value<Expr>::type type;
            };

            /// \brief Return the value of the given terminal expression.
            /// \param expr The terminal expression node.
            /// \pre <tt>is_expr\<Expr\>::value</tt> is \c true
            /// \pre <tt>0 == Expr::proto_arity::value</tt>
            /// \return <tt>proto::value(expr)</tt>
            /// \throw nothrow
            template<typename Expr>
            BOOST_FORCEINLINE
            typename result_of::value<Expr &>::type
            operator ()(Expr &e) const
            {
                return e.proto_base().child0;
            }

            /// \overload
            ///
            template<typename Expr>
            BOOST_FORCEINLINE
            typename result_of::value<Expr const &>::type
            operator ()(Expr const &e) const
            {
                return e.proto_base().child0;
            }
        };

        /// \brief A callable PolymorphicFunctionObject that is
        /// equivalent to the \c left() function.
        struct left
        {
            BOOST_PROTO_CALLABLE()

            template<typename Sig>
            struct result;

            template<typename This, typename Expr>
            struct result<This(Expr)>
            {
                typedef typename result_of::left<Expr>::type type;
            };

            /// \brief Return the left child of the given binary expression.
            /// \param expr The expression node.
            /// \pre <tt>is_expr\<Expr\>::value</tt> is \c true
            /// \pre <tt>2 == Expr::proto_arity::value</tt>
            /// \return <tt>proto::left(expr)</tt>
            /// \throw nothrow
            template<typename Expr>
            BOOST_FORCEINLINE
            typename result_of::left<Expr &>::type
            operator ()(Expr &e) const
            {
                return e.proto_base().child0;
            }

            /// \overload
            ///
            template<typename Expr>
            BOOST_FORCEINLINE
            typename result_of::left<Expr const &>::type
            operator ()(Expr const &e) const
            {
                return e.proto_base().child0;
            }
        };

        /// \brief A callable PolymorphicFunctionObject that is
        /// equivalent to the \c right() function.
        struct right
        {
            BOOST_PROTO_CALLABLE()

            template<typename Sig>
            struct result;

            template<typename This, typename Expr>
            struct result<This(Expr)>
            {
                typedef typename result_of::right<Expr>::type type;
            };

            /// \brief Return the right child of the given binary expression.
            /// \param expr The expression node.
            /// \pre <tt>is_expr\<Expr\>::value</tt> is \c true
            /// \pre <tt>2 == Expr::proto_arity::value</tt>
            /// \return <tt>proto::right(expr)</tt>
            /// \throw nothrow
            template<typename Expr>
            BOOST_FORCEINLINE
            typename result_of::right<Expr &>::type
            operator ()(Expr &e) const
            {
                return e.proto_base().child1;
            }

            template<typename Expr>
            BOOST_FORCEINLINE
            typename result_of::right<Expr const &>::type
            operator ()(Expr const &e) const
            {
                return e.proto_base().child1;
            }
        };

    }

    /// \brief A function that wraps non-Proto expression types in Proto
    /// terminals and leaves Proto expression types alone.
    ///
    /// The <tt>as_expr()</tt> function turns objects into Proto terminals if
    /// they are not Proto expression types already. Non-Proto types are
    /// held by value, if possible. Types which are already Proto types are
    /// left alone and returned by reference.
    ///
    /// This function can be called either with an explicitly specified
    /// \c Domain parameter (i.e., <tt>as_expr\<Domain\>(t)</tt>), or
    /// without (i.e., <tt>as_expr(t)</tt>). If no domain is
    /// specified, \c default_domain is assumed.
    ///
    /// If <tt>is_expr\<T\>::value</tt> is \c true, then the argument is
    /// returned unmodified, by reference. Otherwise, the argument is wrapped
    /// in a Proto terminal expression node according to the following rules.
    /// If \c T is a function type, let \c A be <tt>T &</tt>. Otherwise, let
    /// \c A be the type \c T stripped of cv-qualifiers. Then, \c as_expr()
    /// returns <tt>Domain()(terminal\<A\>::type::make(t))</tt>.
    ///
    /// \param t The object to wrap.
    template<typename T>
    BOOST_FORCEINLINE
    typename add_const<typename result_of::as_expr<T, default_domain>::type>::type
    as_expr(T &t BOOST_PROTO_DISABLE_IF_IS_CONST(T) BOOST_PROTO_DISABLE_IF_IS_FUNCTION(T))
    {
        return default_domain::as_expr<T>()(t);
    }

    /// \overload
    ///
    template<typename T>
    BOOST_FORCEINLINE
    typename add_const<typename result_of::as_expr<T const, default_domain>::type>::type
    as_expr(T const &t)
    {
        return default_domain::as_expr<T const>()(t);
    }

    /// \overload
    ///
    template<typename Domain, typename T>
    BOOST_FORCEINLINE
    typename add_const<typename result_of::as_expr<T, Domain>::type>::type
    as_expr(T &t BOOST_PROTO_DISABLE_IF_IS_CONST(T) BOOST_PROTO_DISABLE_IF_IS_FUNCTION(T))
    {
        return typename Domain::template as_expr<T>()(t);
    }

    /// \overload
    ///
    template<typename Domain, typename T>
    BOOST_FORCEINLINE
    typename add_const<typename result_of::as_expr<T const, Domain>::type>::type
    as_expr(T const &t)
    {
        return typename Domain::template as_expr<T const>()(t);
    }

    /// \brief A function that wraps non-Proto expression types in Proto
    /// terminals (by reference) and returns Proto expression types by
    /// reference
    ///
    /// The <tt>as_child()</tt> function turns objects into Proto terminals if
    /// they are not Proto expression types already. Non-Proto types are
    /// held by reference. Types which are already Proto types are simply
    /// returned as-is.
    ///
    /// This function can be called either with an explicitly specified
    /// \c Domain parameter (i.e., <tt>as_child\<Domain\>(t)</tt>), or
    /// without (i.e., <tt>as_child(t)</tt>). If no domain is
    /// specified, \c default_domain is assumed.
    ///
    /// If <tt>is_expr\<T\>::value</tt> is \c true, then the argument is
    /// returned as-is. Otherwise, \c as_child() returns
    /// <tt>Domain()(terminal\<T &\>::type::make(t))</tt>.
    ///
    /// \param t The object to wrap.
    template<typename T>
    BOOST_FORCEINLINE
    typename add_const<typename result_of::as_child<T, default_domain>::type>::type
    as_child(T &t BOOST_PROTO_DISABLE_IF_IS_CONST(T) BOOST_PROTO_DISABLE_IF_IS_FUNCTION(T))
    {
        return default_domain::as_child<T>()(t);
    }

    /// \overload
    ///
    template<typename T>
    BOOST_FORCEINLINE
    typename add_const<typename result_of::as_child<T const, default_domain>::type>::type
    as_child(T const &t)
    {
        return default_domain::as_child<T const>()(t);
    }

    /// \overload
    ///
    template<typename Domain, typename T>
    BOOST_FORCEINLINE
    typename add_const<typename result_of::as_child<T, Domain>::type>::type
    as_child(T &t BOOST_PROTO_DISABLE_IF_IS_CONST(T) BOOST_PROTO_DISABLE_IF_IS_FUNCTION(T))
    {
        return typename Domain::template as_child<T>()(t);
    }

    /// \overload
    ///
    template<typename Domain, typename T>
    BOOST_FORCEINLINE
    typename add_const<typename result_of::as_child<T const, Domain>::type>::type
    as_child(T const &t)
    {
        return typename Domain::template as_child<T const>()(t);
    }

    /// \brief Return the Nth child of the specified Proto expression.
    ///
    /// Return the Nth child of the specified Proto expression. If
    /// \c N is not specified, as in \c child(expr), then \c N is assumed
    /// to be <tt>mpl::long_\<0\></tt>. The child is returned by
    /// reference.
    ///
    /// \param expr The Proto expression.
    /// \pre <tt>is_expr\<Expr\>::value</tt> is \c true.
    /// \pre \c N is an MPL Integral Constant.
    /// \pre <tt>N::value \< Expr::proto_arity::value</tt>
    /// \throw nothrow
    /// \return A reference to the Nth child
    template<typename N, typename Expr>
    BOOST_FORCEINLINE
    typename result_of::child<Expr &, N>::type
    child(Expr &e BOOST_PROTO_DISABLE_IF_IS_CONST(Expr))
    {
        return result_of::child<Expr &, N>::call(e);
    }

    /// \overload
    ///
    template<typename N, typename Expr>
    BOOST_FORCEINLINE
    typename result_of::child<Expr const &, N>::type
    child(Expr const &e)
    {
        return result_of::child<Expr const &, N>::call(e);
    }

    /// \overload
    ///
    template<typename Expr2>
    BOOST_FORCEINLINE
    typename detail::expr_traits<typename Expr2::proto_base_expr::proto_child0>::reference
    child(Expr2 &expr2 BOOST_PROTO_DISABLE_IF_IS_CONST(Expr2))
    {
        return expr2.proto_base().child0;
    }

    /// \overload
    ///
    template<typename Expr2>
    BOOST_FORCEINLINE
    typename detail::expr_traits<typename Expr2::proto_base_expr::proto_child0>::const_reference
    child(Expr2 const &expr2)
    {
        return expr2.proto_base().child0;
    }

    /// \brief Return the Nth child of the specified Proto expression.
    ///
    /// Return the Nth child of the specified Proto expression. The child
    /// is returned by reference.
    ///
    /// \param expr The Proto expression.
    /// \pre <tt>is_expr\<Expr\>::value</tt> is \c true.
    /// \pre <tt>N \< Expr::proto_arity::value</tt>
    /// \throw nothrow
    /// \return A reference to the Nth child
    template<long N, typename Expr>
    BOOST_FORCEINLINE
    typename result_of::child_c<Expr &, N>::type
    child_c(Expr &e BOOST_PROTO_DISABLE_IF_IS_CONST(Expr))
    {
        return result_of::child_c<Expr &, N>::call(e);
    }

    /// \overload
    ///
    template<long N, typename Expr>
    BOOST_FORCEINLINE
    typename result_of::child_c<Expr const &, N>::type
    child_c(Expr const &e)
    {
        return result_of::child_c<Expr const &, N>::call(e);
    }

    /// \brief Return the value stored within the specified Proto
    /// terminal expression.
    ///
    /// Return the value stored within the specified Proto
    /// terminal expression. The value is returned by
    /// reference.
    ///
    /// \param expr The Proto terminal expression.
    /// \pre <tt>N::value == 0</tt>
    /// \throw nothrow
    /// \return A reference to the terminal's value
    template<typename Expr>
    BOOST_FORCEINLINE
    typename result_of::value<Expr &>::type
    value(Expr &e BOOST_PROTO_DISABLE_IF_IS_CONST(Expr))
    {
        return e.proto_base().child0;
    }

    /// \overload
    ///
    template<typename Expr>
    BOOST_FORCEINLINE
    typename result_of::value<Expr const &>::type
    value(Expr const &e)
    {
        return e.proto_base().child0;
    }

    /// \brief Return the left child of the specified binary Proto
    /// expression.
    ///
    /// Return the left child of the specified binary Proto expression. The
    /// child is returned by reference.
    ///
    /// \param expr The Proto expression.
    /// \pre <tt>is_expr\<Expr\>::value</tt> is \c true.
    /// \pre <tt>2 == Expr::proto_arity::value</tt>
    /// \throw nothrow
    /// \return A reference to the left child
    template<typename Expr>
    BOOST_FORCEINLINE
    typename result_of::left<Expr &>::type
    left(Expr &e BOOST_PROTO_DISABLE_IF_IS_CONST(Expr))
    {
        return e.proto_base().child0;
    }

    /// \overload
    ///
    template<typename Expr>
    BOOST_FORCEINLINE
    typename result_of::left<Expr const &>::type
    left(Expr const &e)
    {
        return e.proto_base().child0;
    }

    /// \brief Return the right child of the specified binary Proto
    /// expression.
    ///
    /// Return the right child of the specified binary Proto expression. The
    /// child is returned by reference.
    ///
    /// \param expr The Proto expression.
    /// \pre <tt>is_expr\<Expr\>::value</tt> is \c true.
    /// \pre <tt>2 == Expr::proto_arity::value</tt>
    /// \throw nothrow
    /// \return A reference to the right child
    template<typename Expr>
    BOOST_FORCEINLINE
    typename result_of::right<Expr &>::type
    right(Expr &e BOOST_PROTO_DISABLE_IF_IS_CONST(Expr))
    {
        return e.proto_base().child1;
    }

    /// \overload
    ///
    template<typename Expr>
    BOOST_FORCEINLINE
    typename result_of::right<Expr const &>::type
    right(Expr const &e)
    {
        return e.proto_base().child1;
    }

    /// INTERNAL ONLY
    ///
    template<typename Domain>
    struct is_callable<functional::as_expr<Domain> >
      : mpl::true_
    {};

    /// INTERNAL ONLY
    ///
    template<typename Domain>
    struct is_callable<functional::as_child<Domain> >
      : mpl::true_
    {};

    /// INTERNAL ONLY
    ///
    template<long N>
    struct is_callable<functional::child_c<N> >
      : mpl::true_
    {};

    /// INTERNAL ONLY
    ///
    template<typename N>
    struct is_callable<functional::child<N> >
      : mpl::true_
    {};

}}

#if defined(_MSC_VER)
# pragma warning(pop)
#endif

#endif