Conditionals

These involve if and switch statements.

There are no else statements in Yul.

if

// SPDX-License-Identifier: GPL-3.0
pragma solidity ^0.8.0;

contract Yul {
    // Is x greater than or equal to 10?
    function ifElse(uint256 x) public pure returns (bytes32) {
        assembly {
            let res
            if lt(x, 10) { res := 0 }
            if eq(x, 10) { res := 1 }
            if gt(x, 10) { res := 1 }
            
            mstore(0x80, res)
            return(0x80, 0x20)
        }
    }
}

lt(a, b) returns true if a < b. gt(a, b) returns true if a > b. eq(a, b) returns true if a == b.

switch

// SPDX-License-Identifier: GPL-3.0
pragma solidity ^0.8.0;

contract Yul {
    // Is x greater than or equal to 80?
    function switch(uint256 x) public pure returns (bytes32) {
        assembly {
            let isTrue
            
            switch gt(x, 79)
            case 1 { isTrue := 0x01 }
            default { isTrue := 0x00 }
            
            mstore(0x80, isTrue)
            return(0x80, 0x20)
        }
    }
}