Question about variable called in Library

[Yip Sin Hang]

I would like to know that , Can I call a variable in a ex4(Libraries) into mq4 file ? 

For example : If I put this in Libraries and compile it 

//+------------------------------------------------------------------+
//|                                                        Happy.mq4 |
//|                        Copyright 2017, MetaQuotes Software Corp. |
//|                                             https://www.mql5.com |
//+------------------------------------------------------------------+
#property library
#property copyright "Copyright 2017, MetaQuotes Software Corp."
#property link      "https://www.mql5.com"
#property version   "1.00"
#property strict


string Happy="Helloworld";

and than How can I call the variable and get the string "Helloworld" in the mq4 which in Experts ?

I have try many different way but I can not call the variable in ex4 from Libraries 

#import "Happy.ex4"
// I have no idea how can I call the string Happy , need help . 
#import

[Alain Verleyen]

Library :

string AreWeHappy() export
  {
   return(Happy);
  }

Import :

#import "Happy.ex4"
string AreWeHappy();
#import

[Yip Sin Hang]

Alain Verleyen:

Library :

Import :

Thanks for your reply . and I have found another way to do it :) 

Library :

string Happy(string &hy){
      return(hy);
}