const and function

[NavidTak]

  string test (const string &hey) //what dose const do here
{
	return hey;


}
string t (string &hey)
{
	return hey;

}
int main ()
{
	
	string h =  test("hi");
	cout << h;
	h = t("hi"); //doesnt work
	cout<<h;

}

[keskiverto]

"doesn't work" is inaccurate.

A compiler says:

 In function 'int main()':
17:12: error: invalid initialization of non-const reference of type 'std::string& {aka std::basic_string<char>&}' from an rvalue of type 'const char*'
7:8: note: in passing argument 1 of 'std::string t(std::string&)' 

Initialization? Lets give a string object then:

	const std::string foo( "hi" );
	h = t( foo );

Not better:

 In function 'int main()':
18:13: error: invalid initialization of reference of type 'std::string& {aka std::basic_string<char>&}' from expression of type 'const string {aka const std::basic_string<char>}'
7:8: note: in passing argument 1 of 'std::string t(std::string&)' 

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