如何解释“ regex e”行？

Question

My function balanceFile returns true if my braces in a file are balanced. For example:

{()} // balanced

{(\\n)} // balanced

{(} // unbalanced

I am using a switch statement provided by my CS professor shown below:

case 8: {
        istringstream iss("{(\n)}");
        assert(balanceFile(iss));
        string str = strCout.str();
        regex e("pair *matching *\\( *and *\\).*\\npair*matching *\\{ *and *\\}");
        assert(regex_search(str, e));}

I am getting the following error:

Assertion failed: regex_search(str,e), file c:\...'

What is causing the assertion failure?

Answer 1

The assertion failure is caused because the thing in assert() is false. That's what assert() does. Literally, the whole point of it is to cause an assertion failure if the thing between the brackets is false.

The reason regex_search(str, e) is false is because the regex e didn't match any part of the string str .