Read char as number value
 

say for example I have a file called key.txt


and I wish to read from this file, digit by digit.

with in being the ifstream object, I would write:


Now, I want this character to be converted to an int of the same value.

so for Example, if I read the '4' character, I want to convert it into a int (4).

the problem is that if I typecast it by doing this:


I get the ASCII value, rather then the numerical value.

How would I accomplish what I want?

Thanks :)

Does C++ use or have an equivilant of the atoi() function?

why can't c++ just use the atoi function?...(uh, it can...it's C++, not B++ or R++, hell.)

out of ignorance, let me suggest something harder than it should be...

if you're reading only ONE character at a time, then you only have to worry about the int values of 0-9. just use a switch to assign the correct integer value to the ascii value. ten cases, trivial problem. i'm sure there's a better way.

use a map.

I'm with using atoi() ... no need to rewrite the wheel...

Also, you can do something like
to get what you want.

i would use that instead of atoi, since this doesn't do more than it needs to do - so it is faster.

Is this for you Password Generator? ;)

I don't know how to deal with files yet, but i know that if u give a "char" variable a number value, it would be converted into an ASCII Character.
EG.

This is What you will get on your screen...


i hope i helped you with this...

char variables contain always numbers. When you give it a value like 'A', the compiler converts it to a number. cout also doesn't convert it. The place where the characters are viewed, will the number be converted. When working in ungraphic mode, the video card converts it.

I believe that atoi() is for strings, not chars.

How about a simple subtraction...


int val = int(n) - 48;

Here's a quick sample...

#include <iostream>
#include <fstream>
#include <cstring>

using namespace std;

int main()
{
string filepath = "D:\\ints.txt";
ifstream in(filepath.c_str());
if(!in.is_open())
{
cerr << "Error opening " << filepath;
return -1;
}

char n;
int via_subtract;
const int ASCII_ZERO = 48;
in.get(n);
while(!in.eof())
{
via_subtract = int(n) - ASCII_ZERO;
cout << "Input = \'" << n << "\'\tvia_subtract = " << via_subtract << "\n";
in.get(n);
}
in.close();

return 0;
}

Hope that helps