【发布时间】：2017-05-01 13:40:29
【问题描述】：
我正在编写 karma 生成器来生成 HTML 页面，但我在使用 column 指令时遇到了不一致的行为。 这很可能是我对其工作原理的理解。
基本上我正在生成一个网格，它要求我在每出现 2 次数据后插入一些分隔符。
以下是我用来进行试运行的基本程序。
#include <boost/config/warning_disable.hpp>
#include <boost/spirit/include/karma.hpp>
#include <boost/fusion/include/struct.hpp>
#include <boost/fusion/include/nview.hpp>
#include <boost/assign/std/vector.hpp>
namespace fusion = boost::fusion;
namespace karma = boost::spirit::karma;
///////////////////////////////////////////////////////////////////////////////
namespace client
{
// Our employee struct
struct employee
{
int num;
std::string datatype;
std::string dataname;
std::string inputicon;
};
// define iterator type
typedef std::back_insert_iterator<std::string> iterator_type;
}
BOOST_FUSION_ADAPT_STRUCT(
client::employee,
(int, num)
(std::string, datatype)
(std::string, dataname)
(std::string, inputicon)
)
///////////////////////////////////////////////////////////////////////////////
int main()
{
std::string str;
// some employees
client::employee john = { 25, "int", "sra_command","fa fa-wrench" };
client::employee mary = { 25, "float", "swt_command","fa fa-wrench" };
client::employee tom = { 25, "double", "msc_command","fa fa-mobile" };
// now make a list of all employees and print them all
std::vector<client::employee> employees;
{
using namespace boost::assign;
employees += john, mary, tom;
}
{
typedef
fusion::result_of::as_nview<client::employee const, 1, 2, 3>::type
names_and_salary;
karma::rule<client::iterator_type, names_and_salary()> small_box =
"<startofblock>" << karma::string << "<after_first>"
<< karma::string << "<after_second>"
<< karma::string << "<after_third>";
std::string generated;
typedef std::back_insert_iterator<std::string> sink_type;
sink_type sink(generated);
karma::generate_delimited(sink, karma::columns(2,karma::string("nth_delimiter"))[small_box % karma::eol],karma::space,employees );
std::cout << generated << std::endl;
}
return 0;
}
上面生成以下输出：
<startofblock>int<after_first>sra_command<after_second>fa fa-wrench<after_third>
nth_delimiter<startofblock>float<after_first>swt_command<after_second>fa fa-wrench<after_third>
nth_delimiter<startofblock>double<after_first>msc_command<after_second>fa fa-mobile<after_third> nth_delimiter
如前所述，第 n 个分隔符出现在每一代之后，而不是每一秒。
预期的输出是
<startofblock>int<after_first>sra_command<after_second>fa fa-wrench<after_third>
<startofblock>float<after_first>swt_command<after_second>fa fa-wrench<after_third>
nth_delimiter<startofblock>double<after_first>msc_command<after_second>fa fa-mobile<after_third>
【问题讨论】：
-
预期输出是什么
-
用 cmets 更新答案
-
有了 columns() 你会得到一个尾随的
nth_delimiter反正。就是这样指定的。 -
是时候再次点击文档来弄清楚如何实现这一点:(
-
我刚刚发布了两种方法，并附赠解释了为什么没有达到您的期望。希望对您有所帮助。
标签： boost boost-spirit boost-spirit-karma