Difference between #define and string?
Hi,
I would like to check what is the difference between #Define and string declaration when it come to myfile.open().
I'm able to compile successfully using the 1st program, however an "error C2664"
occurs when I try to run the 2nd program.
//1st Program
#define FileName "P09.txt"
int main() {
ifstream myfile;
myfile.open(FileName); .
.
.
.
//2nd Program
int main()
{
string FileName="P09.txt";
ifstream myfile;
myfile.open(FileName);
.
.
.
I would like to check what is the difference between #Define and string declaration when it come to myfile.open().
I'm able to compile successfully using the 1st program, however an "error C2664"
occurs when I try to run the 2nd program.
//1st Program
#define FileName "P09.txt"
int main() {
ifstream myfile;
myfile.open(FileName); .
.
.
.
//2nd Program
int main()
{
string FileName="P09.txt";
ifstream myfile;
myfile.open(FileName);
.
.
.
#define FileName "P09.txt" is resolved by the preprocessor which replaces FileName with the literal "P09.txt"
string FileName="P09.txt"; declares a std::string object.The problem is that with the current standard, istream::open takes a
const char* argument ( the type of a string literal ), not a std::string.You can however call string::c_str:
myfile.open(FileName.c_str()); // 2nd program
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