Calling a uint or address as a function in solidity

Question

I am pretty new at both ehtereum and Solidity, so my question might be trivial. But I was not able to find an answer Googling for it. I am looking at the contract code for Bittrex deposit. I found this function

function tokenFallback(address _from, uint _value, bytes _data) {
    (_from);
    (_value);
    (_data);
 }

It looks like it just calls the parameters as functions. Can anyone tell me what is going on?

Also, is there a list somewhere with all the standard stuff you have when coding Solidity. I can find the data types and such, but I didn't know the fallback function was a thing. Are there other standard functions like the fallback function?

Thanks

Answer 1

On the main question: (_from); is not a function call. It's basically a no-op (it does nothing at all). So why use it? I think only to suppress the compiler warning about unused function parameters.

If we remove the parameters from the function body,

function tokenFallback(address _from, uint _value, bytes _data) {
}

putting this into solc gives,

test.solc:2:28: Warning: Unused function parameter. Remove or comment out the variable name to silence this warning.
    function tokenFallback(address _from, uint _value, bytes _data) {
                           ^-----------^
test.solc:2:43: Warning: Unused function parameter. Remove or comment out the variable name to silence this warning.
    function tokenFallback(address _from, uint _value, bytes _data) {
                                          ^---------^
test.solc:2:56: Warning: Unused function parameter. Remove or comment out the variable name to silence this warning.
    function tokenFallback(address _from, uint _value, bytes _data) {
                                                       ^---------^

which is horribly noisy.

As for a comprehensive list of everything you need to know about Solidity, I'm not aware of one. Read a lot of code; ask a lot of questions - doing fine so far!