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1 | [#foldl_reject_incomplete1] |
2 | [section foldl_reject_incomplete1] | |
3 | ||
4 | [h1 Synopsis] | |
5 | ||
6 | template <class P, class State, class ForwardOp> | |
7 | struct foldl_reject_incomplete1; | |
8 | ||
9 | This is a [link parser_combinator parser combinator]. | |
10 | ||
11 | [table Arguments | |
12 | [[Name] [Type]] | |
13 | [[`P`] [[link parser parser]]] | |
14 | [[`State`] [[link metaprogramming_value template metaprogramming value]]] | |
15 | [[`ForwardOp`] [[link metafunction_class template metafunction class] taking two arguments]] | |
16 | ] | |
17 | ||
18 | [h1 Description] | |
19 | ||
20 | The same as [link foldl1 `foldl1`], but once `P` rejects the input, | |
21 | `foldl_reject_incomplete1` checks if `P` consumes any characters before | |
22 | rejecting the input. If so, `foldl_reject_incomplete1` rejects the input with | |
23 | the same error message this last application of `P` returned. Otherwise | |
24 | `foldl_reject_incomplete1` accepts the input and gives the same result as | |
25 | [link foldl1 `foldl1`]. | |
26 | ||
27 | [h1 Header] | |
28 | ||
29 | #include <boost/metaparse/foldl_reject_incomplete1.hpp> | |
30 | ||
31 | [h1 Expression semantics] | |
32 | ||
33 | For any `p` parser, `t` class, `f` metafunction class taking two arguments, | |
34 | `s` compile-time string and `pos` source position | |
35 | ||
36 | foldl_reject_incomplete1<p, t, f>::apply<s, pos> | |
37 | ||
38 | is equivalent to | |
39 | ||
40 | first_of<foldl1<p, t, f>, fail_at_first_char_expected<p> >::apply<s, pos> | |
41 | ||
42 | [h1 Example] | |
43 | ||
44 | #include <boost/metaparse/foldl_reject_incomplete1.hpp> | |
45 | #include <boost/metaparse/lit_c.hpp> | |
46 | #include <boost/metaparse/last_of.hpp> | |
47 | #include <boost/metaparse/token.hpp> | |
48 | #include <boost/metaparse/int_.hpp> | |
49 | #include <boost/metaparse/string.hpp> | |
50 | #include <boost/metaparse/start.hpp> | |
51 | #include <boost/metaparse/get_result.hpp> | |
52 | #include <boost/metaparse/is_error.hpp> | |
53 | ||
54 | #include <boost/mpl/lambda.hpp> | |
55 | #include <boost/mpl/plus.hpp> | |
56 | #include <boost/mpl/int.hpp> | |
57 | ||
58 | using namespace boost::metaparse; | |
59 | ||
60 | using int_token = token<int_>; | |
61 | using plus_token = token<lit_c<'+'>>; | |
62 | using plus_int = last_of<plus_token, int_token>; | |
63 | using sum_op = | |
64 | boost::mpl::lambda<boost::mpl::plus<boost::mpl::_1, boost::mpl::_2>>::type; | |
65 | ||
66 | using ints = foldl_reject_incomplete1<plus_int, boost::mpl::int_<11>, sum_op>; | |
67 | ||
68 | static_assert( | |
69 | get_result< | |
70 | ints::apply<BOOST_METAPARSE_STRING("+ 13 + 3 + 21"), start> | |
71 | >::type::value == 48, | |
72 | "ints should sum the numbers" | |
73 | ); | |
74 | ||
75 | static_assert( | |
76 | is_error< | |
77 | ints::apply<BOOST_METAPARSE_STRING("+ 13 + 3 +"), start> | |
78 | >::type::value, | |
79 | "when the last number is missing, it should be an error" | |
80 | ); | |
81 | ||
82 | static_assert( | |
83 | is_error<ints::apply<BOOST_METAPARSE_STRING(""), start>>::type::value, | |
84 | "when no numbers are provided, it should be an error" | |
85 | ); | |
86 | ||
87 | [endsect] | |
88 |