int main() {
vector<string> tab;
tab.push_back("1234");
cout << tab[0][0];// -> 1
if (int(tab[0][0]) == 1) {
cout << "test";
}
}
why does this comparison not work? what am I doing wrong?
4 Answers
'1' the character is not the same as 1 the integer.
To do your comparison write
if (tab[0][0] == '1') {
Specifically when you convert a character to an integer what you get is the encoding of the character. If you are using ASCII (which is very likely) then the encoding of '1' is 49.
Comments
You're confusing numbers (1, 2, 3, ...) and digits ('1', '2', '3', ...).
They look the same when you print them, but they are not the same.
Comments
The expression tab[0][0] will evaluate to the first character of the first string in the tab vector. Note that this is a character representation (probably ASCII, but not necessarily so), which will not have the numerical value of 1 (it will have the value 49 if your system uses ASCII).
So, in your if test, you need to compare the value with a character literal rather than an integer literal, like so:
int main() {
vector<std::string> tab;
tab.push_back("1234");
std::cout << tab[0][0];// -> 1
if (int(tab[0][0]) == '1') { // Compare to the character '1'!
std::cout << "test";
}
}
Comments
If You Want To Convert A String To A Number Use The Function Atoi()
std::string str = "12345";
int num = std::atoi(str.c_str());
// num = 12345
If You Want one Single Character Not a char*
std::string str = "12345";
int num = str[0] - '0';
// num = 1
if (tab[0][0] == std::to_string(1)) {....}because you cannot cast string to intif (tab[0] == std::to_string(1)) {....},tab[0][0]is a character.if (tab[0][0] == '1') {....}would be enough...