token.qbk
1.63 KB
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
[#token]
[section token]
[h1 Synopsis]
template <class P>
struct token;
This is a [link parser_combinator parser combinator].
[table Arguments
[[Name] [Type]]
[[`P`] [[link parser parser]]]
]
[h1 Description]
`token` parses the input using `P` when it succeeds, `token` consumes all
whitespaces afterwards. The result of parsing is the result of `P`.
[h1 Header]
#include <boost/metaparse/token.hpp>
[h1 Expression semantics]
For any `p` parser the following are equivalent:
token<p>
first_of<p, spaces>
[h1 Example]
#include <boost/metaparse/token.hpp>
#include <boost/metaparse/int_.hpp>
#include <boost/metaparse/start.hpp>
#include <boost/metaparse/get_result.hpp>
#include <boost/metaparse/get_remaining.hpp>
#include <boost/metaparse/is_error.hpp>
#include <boost/metaparse/string.hpp>
#include <type_traits>
using namespace boost::metaparse;
using int_token = token<int_>;
static_assert(
get_result<
int_token::apply<BOOST_METAPARSE_STRING("13 "), start>
>::type::value,
"the result of int_token is the number"
);
static_assert(
std::is_same<
BOOST_METAPARSE_STRING(""),
get_remaining<int_token::apply<BOOST_METAPARSE_STRING("13 "), start>>::type
>::type::value,
"token consumes whitespaces after the number"
);
static_assert(
get_result<
int_token::apply<BOOST_METAPARSE_STRING("13"), start>
>::type::value,
"whitespaces after the number are optional"
);
static_assert(
is_error<int_token::apply<BOOST_METAPARSE_STRING("foo"), start>>::type::value,
"when there is no number, token fails"
);
[endsect]