使用正则表达式替换匹配项
Using regex to replace matches in place
我正在尝试进行某种类型的"字符串扩展",用数据库中的字符串替换键。标签的格式为{$<key>}
。
我正在使用<regex>
来尝试完成这项工作,但我遇到了一些后勤问题。我希望能够一次性替换字符串,但修改字符串(s
)可能会使smatch
对象中的迭代器无效。
以下是我或多或少要做的事情:
#include <iostream>
#include <map>
#include <regex>
using namespace std;
int main()
{
map<string, string> m;
m.insert(make_pair("severity", "absolute"));
m.insert(make_pair("experience", "nightmare"));
string s = "This is an {$severity} {$experience}!";
static regex e("\{\$(.*?)\}");
sregex_iterator next(s.begin(), s.end(), e);
sregex_iterator end;
for (; next != end; ++next)
{
auto m_itr = m.find(next->str(1));
if (m_itr == m.end())
{
continue;
}
//TODO: replace expansion tags with strings somehow?
cout << (*next).str(0) << ":" << m_itr->second << endl;
}
}
期望的最终结果是s
读取:
"This is an absolute nightmare!"
我知道我可以在多次传球中完成这种类型的动作,但这似乎有点野蛮。
我在某个地方读到boost::regex
有regex_replace
的一些变体,它允许以下形式的自定义替换功能:
regex_replace(std::string&, regex, std::string(const smatch&))
然而,我目前的版本(1.55)
没有这样的东西。
非常感谢您的帮助!
附言:我可以使用boost
或std
,以有效的为准!
所以,除了我8小时前的评论:
也许相关:用BoostSpirit编译一个简单的解析器,替换字符串片段,如何使用Boost在.ini文件中扩展环境变量,也许最有趣的是将多个替换快速转换为字符串
我看到了再进一步的空间。如果…您需要基于相同的文本模板进行多次替换,但使用不同的替换映射,该怎么办?
由于我最近发现Boost ICL在映射输入字符串的区域方面是有用的,所以我想在这里做同样的事情。
我把事情做得很一般,并使用Spirit进行分析(study
):
template <
typename InputRange,
typename It = typename boost::range_iterator<InputRange const>::type,
typename IntervalSet = boost::icl::interval_set<It> >
IntervalSet study(InputRange const& input) {
using std::begin;
using std::end;
It first(begin(input)), last(end(input));
using namespace boost::spirit::qi;
using boost::spirit::repository::qi::seek;
IntervalSet variables;
parse(first, last, *seek [ raw [ "{$" >> +alnum >> "}" ] ], variables);
return variables;
}
正如您所看到的,我们只是返回一个interval_set<It>
,这样我们就可以知道变量在哪里,而不是进行任何替换。这就是现在可以用来执行替换字符串映射中的替换的"智慧":
template <
typename InputRange,
typename Replacements,
typename OutputIterator,
typename StudyMap,
typename It = typename boost::range_iterator<InputRange const>::type
>
OutputIterator perform_replacements(InputRange const& input, Replacements const& m, StudyMap const& wisdom, OutputIterator out)
{
using std::begin;
using std::end;
It current(begin(input));
for (auto& replace : wisdom)
{
It l(lower(replace)),
u(upper(replace));
if (current < l)
out = std::copy(current, l, out);
auto match = m.find({l+2, u-1});
if (match == m.end())
out = std::copy(l, u, out);
else
out = std::copy(begin(match->second), end(match->second), out);
current = u;
}
if (current!=end(input))
out = std::copy(current, end(input), out);
return out;
}
现在,一个简单的测试程序是这样的:
int main()
{
using namespace std;
string const input = "This {$oops} is an {$severity} {$experience}!n";
auto const wisdom = study(input);
cout << "Wisdom: ";
for(auto& entry : wisdom)
cout << entry;
auto m = map<string, string> {
{ "severity", "absolute" },
{ "OOPS", "REALLY" },
{ "experience", "nightmare" },
};
ostreambuf_iterator<char> out(cout);
out = 'n';
perform_replacements(input, m, wisdom, out);
// now let's use a case insensitive map, still with the same "study"
map<string, string, ci_less> im { m.begin(), m.end() };
im["eXperience"] = "joy";
perform_replacements(input, im, wisdom, out);
}
打印
Wisdom: {$oops}{$severity}{$experience}
This {$oops} is an absolute nightmare!
This REALLY is an absolute joy!
您可以调用它作为输入字符串文字,使用unordered_map
作为替换等。您可以省略wisdom
,在这种情况下,实现将动态研究它。
完整程序
在Coliru上直播
#include <iostream>
#include <map>
#include <boost/regex.hpp>
#include <boost/icl/interval_set.hpp>
#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/repository/include/qi_seek.hpp>
namespace boost { namespace spirit { namespace traits {
template <typename It>
struct assign_to_attribute_from_iterators<icl::discrete_interval<It>, It, void> {
template <typename ... T> static void call(It b, It e, icl::discrete_interval<It>& out) {
out = icl::discrete_interval<It>::right_open(b, e);
}
};
} } }
template <
typename InputRange,
typename It = typename boost::range_iterator<InputRange const>::type,
typename IntervalSet = boost::icl::interval_set<It> >
IntervalSet study(InputRange const& input) {
using std::begin;
using std::end;
It first(begin(input)), last(end(input));
using namespace boost::spirit::qi;
using boost::spirit::repository::qi::seek;
IntervalSet variables;
parse(first, last, *seek [ raw [ "{$" >> +alnum >> "}" ] ], variables);
return variables;
}
template <
typename InputRange,
typename Replacements,
typename OutputIterator,
typename StudyMap,
typename It = typename boost::range_iterator<InputRange const>::type
>
OutputIterator perform_replacements(InputRange const& input, Replacements const& m, StudyMap const& wisdom, OutputIterator out)
{
using std::begin;
using std::end;
It current(begin(input));
for (auto& replace : wisdom)
{
It l(lower(replace)),
u(upper(replace));
if (current < l)
out = std::copy(current, l, out);
auto match = m.find({l+2, u-1});
if (match == m.end())
out = std::copy(l, u, out);
else
out = std::copy(begin(match->second), end(match->second), out);
current = u;
}
if (current!=end(input))
out = std::copy(current, end(input), out);
return out;
}
template <
typename InputRange,
typename Replacements,
typename OutputIterator,
typename It = typename boost::range_iterator<InputRange const>::type
>
OutputIterator perform_replacements(InputRange const& input, Replacements const& m, OutputIterator out) {
return perform_replacements(input, m, study(input), out);
}
// for demo program
#include <boost/algorithm/string.hpp>
struct ci_less {
template <typename S>
bool operator() (S const& a, S const& b) const {
return boost::lexicographical_compare(a, b, boost::is_iless());
}
};
namespace boost { namespace icl {
template <typename It>
static inline std::ostream& operator<<(std::ostream& os, discrete_interval<It> const& i) {
return os << make_iterator_range(lower(i), upper(i));
}
} }
int main()
{
using namespace std;
string const input = "This {$oops} is an {$severity} {$experience}!n";
auto const wisdom = study(input);
cout << "Wisdom: ";
for(auto& entry : wisdom)
cout << entry;
auto m = map<string, string> {
{ "severity", "absolute" },
{ "OOPS", "REALLY" },
{ "experience", "nightmare" },
};
ostreambuf_iterator<char> out(cout);
out = 'n';
perform_replacements(input, m, wisdom, out);
// now let's use a case insensitive map, still with the same "study"
map<string, string, ci_less> im { m.begin(), m.end() };
im["eXperience"] = "joy";
perform_replacements(input, im, wisdom, out);
}
就地操作
只要确保替换字符串始终比{$pattern}
字符串短(或长度相等),就可以简单地使用input.begin()
作为输出迭代器来调用此函数。
在Coliru上直播
string input1 = "This {$803525c8-3ce4-423a-ad25-cc19bbe8422a} is an {$efa72abf-fe96-4983-b373-a35f70551e06} {$8a10abaa-cc0d-47bd-a8e1-34a8aa0ec1ef}!n",
input2 = input1;
auto m = map<string, string> {
{ "efa72abf-fe96-4983-b373-a35f70551e06", "absolute" },
{ "803525C8-3CE4-423A-AD25-CC19BBE8422A", "REALLY" },
{ "8a10abaa-cc0d-47bd-a8e1-34a8aa0ec1ef", "nightmare" },
};
input1.erase(perform_replacements(input1, m, input1.begin()), input1.end());
map<string, string, ci_less> im { m.begin(), m.end() };
im["8a10abaa-cc0d-47bd-a8e1-34a8aa0ec1ef"] = "joy";
input2.erase(perform_replacements(input2, im, input2.begin()), input2.end());
std::cout << input1
<< input2;
打印
This {$803525c8-3ce4-423a-ad25-cc19bbe8422a} is an absolute nightmare!
This REALLY is an absolute joy!
请注意,您不能(显然)再次在同一个输入模板上重复使用相同的"智慧",因为它将被修改。
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