CODEWITHSUNDEEP
c++if-statementfile-ioconditional-statements
Bapkinz
Bapkinz

Reputation: 5

Check if the next value extracted by >> is going to be a string or int

This seems like it should be ridiculously simple, but I can't figure it out. So I'm reading in values from a file, and I need to know if the next input from that file is going to be a string or an int. Something along the lines of:

if(next command from file is an int){ do this; }
else{ do this; }

here's the code I have so far:

while (!(myFile.eof())) {

    char inPeek = myFile.peek();
    int input;
    string command;

    if (isdigit(inPeek)) {
        int input;
        myFile >> input;

        if (command == "push") {
            MyStack.push(input);
            cout << "Pushed " << input << endl;
        }
        else {
            MyQueue.append(input);
            cout << "Appended " << input << endl;
        }
    }
    else {
        myFile >> command;

        if (command == "pop") {
            MyStack.pop();
            cout << "Popped" << endl;
        }
        if (command == "serve") {
            MyQueue.serve();
            cout << "Served" << endl;
        }
    }
}

But if(isdigit(inPeek)) never returns true. The file that I'm reading from looks like this essentially like this:

append 10
serve
append 20
append 30
serve
push 10
push 50
push 20
push 20
pop

Upvotes: 0

Views: 66

Answers (1)

Emi H&#246;ss
Emi H&#246;ss

Reputation: 86

You can't. There's no a way to know the type of a stream of bytes.

The input is read as a stream of bytes and that stream could be interpreted as a number, a character or a string (or whatever you want).

As PRP said, you should read the input as a string and check inside your program whether your commands need some other input or not.

Also, the function 'isdigit' will return true when the byte read is between 0 and 9.

Upvotes: 1

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