Convert string to int

[vbaswant]

Hello everyone

Could anyone please tell why does the following code not convert the string into int? When I pass a hard coded string e-g "123456" then the code below works, but when I pass a string element from a string type vector, the code doesn't work.

class.h

class cls
{
	public:
	template <class T> bool from_string(T& t, const std::string& s, std::ios_base& (*f)(std::ios_base&)); 
};

class.cpp

template <class T> bool cls::from_string(T& t, const std::string& s, std::ios_base& (*f)(std::ios_base&))
{
	std::istringstream iss(s);
	return !(iss >> f >> t).fail();
}

void cls::somefunct()
{
	int i;
	string strn = vector[1];
	if(from_string(i, std::string(strn), std::dec))
	{
		std::cout << "i: " << i << std::endl;
	}
	else
	{
		std::cout << "from_string failed" << std::endl;
	}
}

[kfmfe04]

string str;
int i = atoi( str.c_str() );

is easier, but if you insist on C++, you should correct Lines 8 and 11.
There may be other errors, but that's what I eyeball atm.

[vbaswant]

Thanks kfmfe04

I've also tried this but the result is not what I want.

vector[1] = "00181170323230"

string str = vector[1];

int i = atoi( str.c_str() );

cout << "atoi: " << i << endl;

result is
atoi: 781696798

[kfmfe04]

well, I hope you realize that a C/C++ int does not have infinite precision.

if you intend to pass in strings that big, then:

#include <vector>
#include <string>
#include <iostream>

using namespace std;

static vector<string> vec;

main()
{
  vec.push_back( "00181170323230" );
  long l = strtol(vec[0].c_str(), (char **)NULL, 10);
  cout << "strtol: " << l << endl;
}

strtol: 181170323230

NOTE: also, if you are using an STL vector, realize that it is 0-based and not 1-based. Also, you will have to use push_back() to insert values, if the vector started off empty. Please read up on stl vectors, but if you already know all this, then you can ignore me.

[vbaswant]

Thanks a lot. That worked and thanks for all your suggestions :-).

vector[1] = "00181170323230" was just an example to show that index [1] holds "00181170323230" value.

THANKS

[kfmfe04]

np - btw, there are some C++ purists who will only use C++ constructs - I'm not one of them =)

gl w/your coding

[vbaswant]

Thank you (:-)