Question

I have a method search that I want to feed an input stream and then put output on an output stream.

void search(std::istream & is, std::ostream & os);

For now I’d like to do this with cin/cout. From the command prompt:

a.out < input_file.txt

In main, I try to do this by passing cin/cout to the search() method.

X.search(std::cin, std::cout);

I get the following error when I compile and link (XCode):

Line Location Tool:0: collect2: ld returned 1 exit status
Line Location Tool:0: symbol(s) not found
Line Location Tool:0: _main in main.o
Line Location Tool:0: "X::search(std::basic_istream<char, std::char_traits<char> >&,
   std::basic_ostream<char, std::char_traits<char> >&)", referenced from:

Is there anything different I need to be doing for cin/cout? I cannot figure out how to resolve this error.

Answer 1

This compiles and runs fine for me in xcode (c++ cmdline new project wizard), looks like you’re missing an #include <iostream> or main, or a definition of your X class.

#include <iostream>

void foo( std::istream &is, std::ostream &os )
{
    std::string s;
    while ( getline( is, s, '\n' ) )
    {
        os << s;
    }
}

int main (int argc, char * const argv[]) {
    // insert code here...
    std::cout << "Hello, World!\n";
    foo( std::cin, std::cout );

    return 0;
}