56 lines
1.6 KiB
Plaintext
56 lines
1.6 KiB
Plaintext
[/==============================================================================
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Copyright (C) 2001-2015 Joel de Guzman
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Copyright (C) 2001-2011 Hartmut Kaiser
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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===============================================================================/]
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[section Number List Redux - list syntax]
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So far, we've been using the syntax:
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double_ >> *(',' >> double_)
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to parse a comma-delimited list of numbers. Such lists are common in parsing and
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Spirit provides a simpler shortcut for them. The expression above can be
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simplified to:
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double_ % ','
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read as: a list of doubles separated by `','`.
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This sample, again a variation of our previous example, demonstrates just that:
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template <typename Iterator>
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bool parse_numbers(Iterator first, Iterator last, std::vector<double>& v)
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{
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using x3::double_;
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using x3::phrase_parse;
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using x3::_attr;
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using ascii::space;
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auto push_back = [&](auto& ctx){ v.push_back(_attr(ctx)); };
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bool r = phrase_parse(first, last,
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// Begin grammar
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(
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double_[push_back] % ','
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)
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,
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// End grammar
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space);
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if (first != last) // fail if we did not get a full match
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return false;
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return r;
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}
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The full cpp file for this example can be found here:
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[@../../../example/x3/num_list/num_list3.cpp num_list3.cpp]
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[endsect]
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