Skipping expected characters like scanf() with cin

Question

How to achieve scanf(\"%d # %d\",&a,&b);sort of effect with cin in C++ ?

Answer 1

There isn't a direct function inside the istream class that mimics it, unfortunately. There are functions that you might be able to use to manipulate the stream and get the correct input, but I'm not familiar with how they work so I couldn't tell you how.

My best suggestion on how I would personally do it is to use getline() to put the input into a string and then from there I would do a few checks to see if it matches the format. So in your case I would grab the first substring up until the first space, make sure it's a valid decimal, check to make sure the pound sign ('#') is in the correct spot, then grab the ending number to make sure it's valid. If any one of those three objects are incorrect I would set some boolean variable to false to kick out or return or something to indicate that the input was invalid and not the correct format.

Pseudo Code:

...

getline(cin,myStr);

while(!formatCheck(myStr))
{
    cout<<"Not valid format for input";
    getline(cin,myStr);
}

...

bool formatCheck(string str)
{
    string firstPart=str.subString(0,firstSpaceLocation);
    string middle=str[firstSpaceLocation+1];
    string lastPart=str.subString(firstSpaceLocation+3,end);

    if(first part not a valid number || middle!="#" || last part not a valid number)
    {
        return false;
    }

    return true;
}