I would like to know what is the easiest way to convert an int to C++ style string and from C++ style string to int.
edit
Thank you very much. When converting form string to int what happens if I pass a char string ? (ex: "abce").
Thanks & Regards,
Mousey
Probably the easiest is to use operator<< and operator>> with a stringstream (you can initialize a stringstream from a string, and use the stream's .str() member to retrieve a string after writing to it.
Boost has a lexical_cast that makes this particularly easy (though hardly a paragon of efficiency). Normal use would be something like int x = lexical_cast<int>(your_string);
You can change "%x" specifier to "%d" or any other format supported by sprintf. Ensure to appropriately adjust the buffer size 'buf'
int main(){ char buf[sizeof(int)*2 + 1]; int x = 0x12345678; sprintf(buf, "%x", x); string str(buf); int y = atoi(str.c_str()); } EDIT 2:
int main(){ char buf[sizeof(int)*2 + 1]; int x = 42; sprintf(buf, "%x", x); string str(buf); //int y = atoi(str.c_str()); int y = static_cast<int>(strtol(str.c_str(), NULL, 16)); } 
sprintf(buf, "%x", 42); puts "2a" into buf. atoi("2a") is going to return 2 not 42.
This is to convert string to number.
#include "stdafx.h" #include <iostream> #include <string> #include <sstream> int convert_string_to_number(const std::string& st) { std::istringstream stringinfo(st); int num = 0; stringinfo >> num; return num; } int main() { int number = 0; std::string number_as_string("425"); number = convert_string_to_number(number_as_string); std::cout << "The number is " << number << std::endl; std::cout << "Number of digits are " << number_as_string.length() << std::endl; } Like wise, the following is to convert number to string.
#include "stdafx.h" #include <iostream> #include <string> #include <sstream> std::string convert_number_to_string(const int& number_to_convert) { std::ostringstream os; os << number_to_convert; return (os.str()); } int main() { int number = 425; std::string stringafterconversion; stringafterconversion = convert_number_to_string(number); std::cout << "After conversion " << stringafterconversion << std::endl; std::cout << "Number of digits are " << stringafterconversion.length() << std::endl; } 
#include "stdafx.h"? You need the other three, but you can definitely do without stdafx.h. Oh, and main is supposed to return an integer.
main is a special case and may have the return 0; omitted resulting in the same effect as if you had put it there.
convert_string_to_number("blah")? As it is, this will silently fail and return the same as if I'd called convert_string_to_number("0"). That''s a definitive -1 from me.
Use atoi to convert a string to an int. Use a stringstream to convert the other way.
atoi, at least use strtol, which can at least indicate when there's an error.