Using stringstream in C++

[bnchs]

I have an input file that has lines containing integers, characters and strings that has to be parsed to extract information from it. I am using an istringstream to do this but am having problems getting it to work.

The lines can look like:

2 : 2 5 5 8
2 = 2 * 2
show 2

I already have a part working where the char colon contains ':' and poly and location are integers

if (iss >> poly >> colon)
{
location = poly;

while(iss >> coeff >> exp)
{
//do something
}
}

So this correctly extracts the information from a line in the form of the first line from my example lines.

In the following example, show is declared as a string containing "show" but it does not work.

 if(iss >> show >> poly)
   {      
    locationOfPoly = poly;
    cout <<"Poly[" << locationOfPoly << "] = " << Poly[locationOfPoly] << "\n";
   }
 

Can an istringstream be used in this way? Or, in other words is it possible to check if the istringstream reads something in particular as I am trying to do above? Thanks.

[weaknessforcats]

The >> operator is for formatted input. That is, you already know the being extracted.

If you don't and extract an int into a char, for example, you will get the stream failbit set and the >> operator just returns without doing anything - and laving the bad data in the stream. All subsequent >> calls test the failbit first, and of set, they return without doing any thing.

If this is text input, you may want to just get trhe file a byte at a time so you can interogate wahet you got and make a decision at that time.