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#include <openpose/utilities/errorAndLog.hpp>
#include <openpose/utilities/string.hpp>
namespace op
{
template<typename T>
std::string toFixedLengthString(const T number, const unsigned long long stringLength)
{
try
{
const auto numberAsString = std::to_string(number);
if (stringLength > 0)
{
if (number < 0)
error("toFixedLengthString: number cannot be <= 0, in this case it is: " + numberAsString + ".", __LINE__, __FUNCTION__, __FILE__);
const auto zerosToAdd = stringLength - numberAsString.size();
if (zerosToAdd < 0)
{
const auto errorMessage = "toFixedLengthString: number greater than maximum number of digits (stringLength): "
+ numberAsString + " vs. " + std::to_string(stringLength) + ".";
error(errorMessage, __LINE__, __FUNCTION__, __FILE__);
}
return { std::string(zerosToAdd, '0') + numberAsString};
}
else
return numberAsString;
}
catch (const std::exception& e)
{
error(e.what(), __LINE__, __FUNCTION__, __FILE__);
return "";
}
}
// Signed
template std::string toFixedLengthString<char>(const char number, const unsigned long long stringLength);
template std::string toFixedLengthString<signed char>(const signed char number, const unsigned long long stringLength);
template std::string toFixedLengthString<short>(const short number, const unsigned long long stringLength);
template std::string toFixedLengthString<int>(const int number, const unsigned long long stringLength);
template std::string toFixedLengthString<long>(const long number, const unsigned long long stringLength);
template std::string toFixedLengthString<long long>(const long long number, const unsigned long long stringLength);
// Unsigned
template std::string toFixedLengthString<unsigned char>(const unsigned char number, const unsigned long long stringLength);
template std::string toFixedLengthString<unsigned short>(const unsigned short number, const unsigned long long stringLength);
template std::string toFixedLengthString<unsigned int>(const unsigned int number, const unsigned long long stringLength);
template std::string toFixedLengthString<unsigned long>(const unsigned long number, const unsigned long long stringLength);
template std::string toFixedLengthString<unsigned long long>(const unsigned long long number, const unsigned long long stringLength);
}
这是src文件,他在头文件中有相应的功能。为什么他需要定义下面的东西,而不是将整个模板函数放在头文件中,根据SO上的其他帖子,应该是人们如何定义模板函数。为什么要用C++定义模板函数?
你不需要这么定义它。它会更有意义的是它在头文件中。它可以用这种方式来定义,但这意味着您需要为其每次使用提供一个实例。 – Tas
请参阅https://stackoverflow.com/questions/2351148/explicit-instantiation-when-is-it-used和https://stackoverflow.com/questions/13068993/when-would-you-use-template-explicit-实例 – Curious