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