c ++ 11的序列zip函数? [英] Sequence-zip function for c++11?
本文介绍了c ++ 11的序列zip函数?的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
使用新的基于范围的for循环,我们可以为(auto x:Y){} $编写代码
b $ b
哪个IMO是巨大的改进
for(std :: vector< int> iter iterator x = Y.begin(); x!= Y.end ++ x){}
可以用于循环两个同时循环,如Pythons zip
function?对于不熟悉Python的人,代码如下:
Y1 = [1,2,3]
Y2 = [4 ,5,6,7]
for x1,x2 in zip(Y1,Y2):
print x1,x2
提供输出(1,4)(2,5)(3,6)
<如果输入容器的长度不一样,boost :: zip_iterator的Boost 1.48.0会导致未定义的行为。如果输入容器的长度不一样,boost :: zip_iterator会导致未定义的行为。 (可能会崩溃或重复超过结束)。
code>:
#include< boost / iterator / zip_iterator.hpp>
#include< boost / range.hpp>
template< typename ... T>
auto zip(const T& ... container) - > boost :: iterator_range< boost :: zip_iterator< decltype(boost :: make_tuple(std :: begin(containers)...))>>
{
auto zip_begin = boost :: make_zip_iterator(boost :: make_tuple(std :: begin(containers)...));
auto zip_end = boost :: make_zip_iterator(boost :: make_tuple(std :: end(containers)...));
return boost :: make_iterator_range(zip_begin,zip_end);
}
示例:
#include< cstdio>
#include< vector>
#include< list>
int main()
{
std :: vector< int> a {4,5,6};
double b [] = {7,8,9};
std :: list< std :: string> c {a,b,c};
for(auto tup:zip(a,b,c,a))
{
int x,w;
double y;
std :: string z;
boost :: tie(x,y,z,w)= tup;
printf(%d%g%s%d \\\
,x,y,z.c_str(),w);
}
}
这将打印
4 7 a 4
5 8 b 5
6 9 c 6
With the new range-based for loop we can write code like
for(auto x: Y) {}
Which IMO is a huge improvement from (for ex.)
for(std::vector<int>::iterator x=Y.begin(); x!=Y.end(); ++x) {}
Can it be used to loop over two simultaneous loops, like Pythons zip
function? For those unfamiliar with Python, the code:
Y1 = [1,2,3]
Y2 = [4,5,6,7]
for x1,x2 in zip(Y1,Y2):
print x1,x2
Gives as output (1,4) (2,5) (3,6)
解决方案
Warning: boost::zip_iterator as of Boost 1.48.0 will cause undefined behavior if the length of the input containers are not the same (it may crash or iterate beyond the end).
A variadic version of zip
:
#include <boost/iterator/zip_iterator.hpp>
#include <boost/range.hpp>
template <typename... T>
auto zip(const T&... containers) -> boost::iterator_range<boost::zip_iterator<decltype(boost::make_tuple(std::begin(containers)...))>>
{
auto zip_begin = boost::make_zip_iterator(boost::make_tuple(std::begin(containers)...));
auto zip_end = boost::make_zip_iterator(boost::make_tuple(std::end(containers)...));
return boost::make_iterator_range(zip_begin, zip_end);
}
Example:
#include <cstdio>
#include <vector>
#include <list>
int main()
{
std::vector<int> a {4, 5, 6};
double b[] = {7, 8, 9};
std::list<std::string> c {"a", "b", "c"};
for (auto tup : zip(a, b, c, a))
{
int x, w;
double y;
std::string z;
boost::tie(x, y, z, w) = tup;
printf("%d %g %s %d\n", x, y, z.c_str(), w);
}
}
This would print
4 7 a 4 5 8 b 5 6 9 c 6
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