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Martin Perry's questions

Martin Hope
Martin Perry
Asked: 2024-05-29 16:13:59 +0800 CST
  • 9

我有 UTF-8 字符串，我想搜索所有出现的img_(\d+). 我试过原版的

$pattern = '/img_(\d+)/u';
preg_match_all($pattern, $text, $matches, PREG_OFFSET_CAPTURE);

但它给了我错误的模式偏移。

我也尝试过：

mb_internal_encoding('UTF-8');
$pattern = 'img_(\d+)';
mb_ereg_search_init($content, $pattern);

$matches = [];        
while ($result = mb_ereg_search_regs()) {
    $matches[] = [
        'match' => $result[0],
        'offset' => mb_ereg_search_getpos() - mb_strlen($result[0]),
    ];
}

但它给了我与 相同的结果preg_match_all。

但是，当我使用以下命令手动运行搜索时：

$pos = mb_strpos($content, "img_1", 0);

我得到了正确的偏移量。

示例代码：

$str = "příliš žluťoučký img_1 kůn úpěl ďábelské ódy";

$pattern = '/img_(\d+)/u';
preg_match_all($pattern, $str, $matches, PREG_OFFSET_CAPTURE);

print_r($matches); //gives 24 (wrong)

echo mb_strpos($str, "img_1", 0); //gives 17 (correct)

如何解决这个问题？

Martin Hope
Martin Perry
Asked: 2023-09-25 02:20:02 +0800 CST
  • 5

我的 C++20 代码在 MSVC 下运行良好。但是，我的 GCC 版本不支持时区，所以我想使用 Howard Hinnant 库。

#include <chrono>

using LocalTime = std::chrono::time_point<std::chrono::local_t, std::chrono::system_clock::duration>;
//using LocalTime = std::chrono::local_time<std::chrono::system_clock::duration>;

using UtcTime = std::chrono::time_point<std::chrono::system_clock>;

LocalTime UtcToLocal(UtcTime t)
{       
    auto tz = std::chrono::current_zone();
    LocalTime tLocal = tz->to_local(t);
    return tLocal;
}

UtcTime LocalToUtc(LocalTime t)
{
    auto tz = chronoExt::current_zone();
    UtcTime tUtc = tz->to_sys(t);

    return tUtc;
}

如果我将代码更改为：

#include "tz.h"
#include "date.h"

LocalTime UtcToLocal(UtcTime t)
{       
    auto tz = date::current_zone();
    LocalTime tLocal = tz->to_local(t);
    return tLocal;
}

UtcTime LocalToUtc(LocalTime t)
{
    auto tz = date::current_zone();
    UtcTime tUtc = tz->to_sys(t);

    return tUtc;
}

在 MSVC 中我遇到错误：

error C2440: 'initializing': cannot convert from 'std::chrono::time_point<date::local_t,std::chrono::duration<std::chrono::system_clock::rep,std::chrono::system_clock::period>>' to 'std::chrono::time_point<std::chrono::local_t,std::chrono::system_clock::duration>'
message : No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called
error C2672: 'date::time_zone::to_sys': no matching overloaded function found
message : could be 'std::chrono::time_point<std::chrono::system_clock,common_type<_Duration,std::chrono::seconds>::type> date::time_zone::to_sys(std::chrono::time_point<date::local_t,Duration>,date::choose) const'
message : 'std::chrono::time_point<std::chrono::system_clock,common_type<_Duration,std::chrono::seconds>::type> date::time_zone::to_sys(std::chrono::time_point<date::local_t,Duration>,date::choose) const': expects 2 arguments - 1 provided
message : or       'std::chrono::time_point<std::chrono::system_clock,common_type<_Duration,std::chrono::seconds>::type> date::time_zone::to_sys(std::chrono::time_point<date::local_t,Duration>) const'
message : 'std::chrono::time_point<std::chrono::system_clock,common_type<_Duration,std::chrono::seconds>::type> date::time_zone::to_sys(std::chrono::time_point<date::local_t,Duration>) const': could not deduce template argument for 'std::chrono::time_point<date::local_t,Duration>' from 'LocalTime'
c++