How to use std::istream correctly

Question

I want to do the following:

// I want 'is' to be either opened file or stringstream ...
void ParseTokens(const std::istream &is, std::vector<TokenClass> &vToks)
{
    char ch;
    ...
    is >> ch;
    ...
}

The compiler complains:

error: ambiguous overload for ‘operator>>’ in ‘is >> ch’

What do I need to do to make this work?

[edit]
Just a caveat: operator>> gives formatted output - it loses white-space characters (tabs, newlines, etc). To access all the characters, you need to use get() .

Answer 1

Since is >> ch; extracts characters from is , it modifies the stream. Therefore, it can't be const in the function signature, which can cause seemingly irrelevant errors because there's no exact match. Change the function to take a std::istream & .