no operator “<<” matches these operands [duplicate]

Answer 1

You're not including the standard <string> header.

You got [un]lucky that some of its pertinent definitions were accidentally made available by the other standard headers that you did include ... but operator<< was not.

• https://stackoverflow.com/a/20937531/560648

Answer 2

If you want to use std::string reliably, you must #include <string>.

Answer 3

It looks like you're comparing strings incorrectly. To compare a string to another, use the std::string::compare function.

Example

     while ((wrong < MAX_WRONG) && (soFar.compare(THE_WORD) != 0))