|
1 //----------------------------------------------------------------------------- |
|
2 // boost blank.hpp header file |
|
3 // See http://www.boost.org for updates, documentation, and revision history. |
|
4 //----------------------------------------------------------------------------- |
|
5 // |
|
6 // Copyright (c) 2003 |
|
7 // Eric Friedman |
|
8 // |
|
9 // Distributed under the Boost Software License, Version 1.0. (See |
|
10 // accompanying file LICENSE_1_0.txt or copy at |
|
11 // http://www.boost.org/LICENSE_1_0.txt) |
|
12 |
|
13 #ifndef BOOST_BLANK_HPP |
|
14 #define BOOST_BLANK_HPP |
|
15 |
|
16 #include "boost/blank_fwd.hpp" |
|
17 |
|
18 #include <iosfwd> // for std::basic_ostream forward declare |
|
19 |
|
20 #include "boost/detail/templated_streams.hpp" |
|
21 #include "boost/mpl/bool.hpp" |
|
22 #include "boost/type_traits/is_empty.hpp" |
|
23 #include "boost/type_traits/is_pod.hpp" |
|
24 #include "boost/type_traits/is_stateless.hpp" |
|
25 |
|
26 namespace boost { |
|
27 |
|
28 struct blank |
|
29 { |
|
30 }; |
|
31 |
|
32 // type traits specializations |
|
33 // |
|
34 |
|
35 template <> |
|
36 struct is_pod< blank > |
|
37 : mpl::true_ |
|
38 { |
|
39 }; |
|
40 |
|
41 template <> |
|
42 struct is_empty< blank > |
|
43 : mpl::true_ |
|
44 { |
|
45 }; |
|
46 |
|
47 template <> |
|
48 struct is_stateless< blank > |
|
49 : mpl::true_ |
|
50 { |
|
51 }; |
|
52 |
|
53 // relational operators |
|
54 // |
|
55 |
|
56 inline bool operator==(const blank&, const blank&) |
|
57 { |
|
58 return true; |
|
59 } |
|
60 |
|
61 inline bool operator<=(const blank&, const blank&) |
|
62 { |
|
63 return true; |
|
64 } |
|
65 |
|
66 inline bool operator>=(const blank&, const blank&) |
|
67 { |
|
68 return true; |
|
69 } |
|
70 |
|
71 inline bool operator!=(const blank&, const blank&) |
|
72 { |
|
73 return false; |
|
74 } |
|
75 |
|
76 inline bool operator<(const blank&, const blank&) |
|
77 { |
|
78 return false; |
|
79 } |
|
80 |
|
81 inline bool operator>(const blank&, const blank&) |
|
82 { |
|
83 return false; |
|
84 } |
|
85 |
|
86 // streaming support |
|
87 // |
|
88 BOOST_TEMPLATED_STREAM_TEMPLATE(E,T) |
|
89 inline BOOST_TEMPLATED_STREAM(ostream, E,T)& operator<<( |
|
90 BOOST_TEMPLATED_STREAM(ostream, E,T)& out |
|
91 , const blank& |
|
92 ) |
|
93 { |
|
94 // (output nothing) |
|
95 return out; |
|
96 } |
|
97 |
|
98 } // namespace boost |
|
99 |
|
100 #endif // BOOST_BLANK_HPP |