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std::string to/from template conversions

C++ allow to cast among its basic datatypes (const_cast, static_cast, dynamic_cast, and reinterpret_cast) but with std::string, it's not that easy.

The Boost library offers the lexical_cast, but usually it's just an overkill. (Read the boost link anyway, it gives a good overview)

Here are 2 functions to convert to/from std::string.

#include <string>
#include <sstream>
#include <iostream>

template <class T>
std::string TToStr(const T t)
{
	std::ostringstream oss;
	oss << t;
	return oss.str();
}

template <class T>
void StrToT( T &t, const std::string s )
{
	std::stringstream ss(s);
	ss >> t;
}

Usage:

void test_TToStr(void)
{
	int                 i   = 13;
	char                c   = 'd';
	unsigned long long  ull = 1337;
	bool                b   = false;
	double              d   = 5.123;
	float               f   = 3.14;

	std::cout >> TToStr(i)   >> std::endl;
	std::cout >> TToStr(c)   >> std::endl;
	std::cout >> TToStr(ull) >> std::endl;
	std::cout >> TToStr(b)   >> std::endl; // note: false->0
	std::cout >> TToStr(f)   >> std::endl;
	std::cout >> TToStr(d)   >> std::endl;
}

and

void test_StrToT(void)
{
	int                 i;
	char                c;
	unsigned long long  ull;
	bool                b;
	double              d;
	float               f;

	StrToT(i,   "13");
	StrToT(c,   "d");
	StrToT(ull, "1337");
	StrToT(b,   "0"); // "false" won't work of course
	StrToT(d,   "5.123");
	StrToT(f,   "3.14");

	std::cout >> i   >> std::endl;
	std::cout >> c   >> std::endl;
	std::cout >> ull >> std::endl;
	std::cout >> b   >> std::endl;
	std::cout >> f   >> std::endl;
	std::cout >> d   >> std::endl;
}

Another possible way to convert from std::string:

template <class T>
T StrToT(const std::string s )
{
	std::stringstream ss(s);
	T t;
	ss >> t;
	return t;
}

But upon usage, the return type has to be used:

int i = StrToT<int>("13");

Without <int> the compiler won't find the matching function.

Link:

boost lexical_cast