_Follow along with this video:_ --- In this lesson we're going to take the next step in routing our `call data` to the appropriate function! Previously we'd isolated our function selector and we'd said: ``` If f_select == updateHorseNumber -> jump to that data in the contract If f_select == readNumberOfHorses -> jump to that data in the contract ``` Let's look at how we perform these comparisons in Huff. Our function selectors for these functions are as follows: ``` updateHorseNumber = 0xcdfead2e readNumberOfHorses = 0xe026c017 ``` These selectors can be determines by running `cast sig "updateHorseNumber(uint256)"` and `cast sig readNumberOfHorses()` respectfully. Once we have these signatures, there's an op code we can use to check equality, the `EQ` op code! Let's review how it works in [**evm.codes**](https://www.evm.codes/?fork=shanghai) ::image{src='/formal-verification-1/19-opcode-eq/opcode-eq-1.png' style='width: 75%; height: auto;'} As we can see, the `EQ` op code takes the top item on our stack and compares it to the next item in the stack. This op code will return `1` if the values compared are equal and `0` if they are not equal. Let's remind ourselves of our current contract state: ```js #define macro MAIN() = takes(0) returns(0){ 0x00 calldataload 0xe0 shr // [function_selector] } ``` Our stack currently has the isolated `function selector` from our received `calldata` on it, so to perform our comparison we'll need to `PUSH` our function selector to the stack and then execute the `EQ` operation! Our contract (and stack) are going to look this like as a result: ```js #define macro MAIN() = takes(0) returns(0){ 0x00 calldataload 0xe0 shr // [function_selector] 0xcdfead2e // [0xcdfead2e, function_selector] eq // [true_if_func_selector_matches] } ``` Let's next take a look at how to handle when a match is found!