How does a contract know which library to query? For Example in the code below (The code is from solidity docs: https://solidity.readthedocs.io/en/v0.4.24/contracts.html?highlight=library#libraries
pragma solidity ^0.4.22;
library Set {
// We define a new struct datatype that will be used to
// hold its data in the calling contract.
struct Data { mapping(uint => bool) flags; }
// Note that the first parameter is of type "storage
// reference" and thus only its storage address and not
// its contents is passed as part of the call. This is a
// special feature of library functions. It is idiomatic
// to call the first parameter `self`, if the function can
// be seen as a method of that object.
function insert(Data storage self, uint value)
public
returns (bool)
{
if (self.flags[value])
return false; // already there
self.flags[value] = true;
return true;
}
function remove(Data storage self, uint value)
public
returns (bool)
{
if (!self.flags[value])
return false; // not there
self.flags[value] = false;
return true;
}
function contains(Data storage self, uint value)
public
view
returns (bool)
{
return self.flags[value];
}
}
contract C {
Set.Data knownValues;
function register(uint value) public {
// The library functions can be called without a
// specific instance of the library, since the
// "instance" will be the current contract.
require(Set.insert(knownValues, value));
}
// In this contract, we can also directly access knownValues.flags, if we want.
}
How does Contract C know where the Set library is located and what if there are other libraries called Set?
Is there something missing in this code?