What does (a); mean in solidity? [duplicate]

Question

The bittrex contract has the following code.
What does (a); and (val); mean?

contract Token {
    function balanceOf(address a) returns (uint) {
        (a);
        return 0;
    }

    function transfer(address a, uint val) returns (bool) {
        (a);
        (val);
        return false;
    }
}

Answer 1

It doesn't do anything. It just states the variable within brackets, which just evaluates to the value of the variable, but it's assigned to nothing. I compared the gas usage to a version of the contract which has that line commented out and it has identical gas costs to run the function, so it may be ignored by the compiler anyway.

They may have added it to silence compiler warnings about the function parameters not being used.

Answer 2

Is used to avoid compilation warnings as AnAllergyToAnalogy's said.

Another way to do so is to comment the parameters name

function transfer (address /* a */, uint /* Val */) returns (bool)

In this case the body of the function can contain only the return statement.