Question

I opened a .txt file with an ifstream object named input. If a new line starts with a “(” then it doesn’t read it how I want it to. The expected output doesn’t get printed, then it exits the loops. I want it to only jump out of the while loop when it reaches the end of the file. What am I doing wrong? My do while loop and my .txt file are below.

char c;
int i;
do
{
    if(input.peek( ) == '(' || input.peek( ) == ')')
    {
        input >> c;
        cout << c;
    }else if(input.peek( ) == '+' || input.peek( ) == '-' || input.peek( ) == '*' || input.peek( ) == '/')
    {
        input >> c;
        cout << c;
    }else
    {
        input >> i;
        cout << i;
    }

}while(input && input.peek( ) != EOF);

Here is the .txt file, each on a separate line:

(3)
(3)
4
(5+7)-(5*3)

This is my output:

 (3)3

Answer 1

So, I’m pretty certain that the problem is that input.peek() is returning a newline after ')' has been read. Then input >> i; doesn’t read a number, and i remains the value it had before, so the output is 3. You could quickly try this by adding i = 42; before input >> i; – if the output becomes (3)42, then I’m right.

If I’m right, you will want to add a bit of code to handle isspace() or something similar.

May I also suggest that you do something like cpeek = input.peek();, before the first if, and then use if (cpeek == '(' || cpeek == ')')... etc.