DecimalsTest.sol

pragma solidity ^0.4.19;

contract DecimalsTest {
    
    uint256 public decimals256;
    uint256 public totalSupply256_AsExpected_1;
    uint256 public totalSupply256_AsExpected_2;
    
    uint8 public decimals8;
    uint256 public totalSupply256_Unexpected_1;
    uint256 public totalSupply256_Unexpected_2;

    uint256 public decimals256_Unexpected_1;
    uint256 public decimals256_Unexpected_2;

    function DecimalsTest() public {
        
        uint256 _decimals256        = 18;
        uint8   _decimals8          = 18;
        uint256 _initialSupply256   = 500000;
        
        // memory
        totalSupply256_AsExpected_1 = _initialSupply256 * (10 ** _decimals256);
        
        // same result with storage
        decimals256 = _decimals256;
        totalSupply256_AsExpected_2 = _initialSupply256 * (10 ** decimals256);

        // memory
        totalSupply256_Unexpected_1 = _initialSupply256 * (10 ** _decimals8);
        
        // same result with storage
        decimals8 = _decimals8;
        totalSupply256_Unexpected_2 = _initialSupply256 * (10 ** decimals8);
        
        // memory
        decimals256_Unexpected_1 = 10 ** _decimals8;
        
        // same result with storage
        decimals256_Unexpected_2 = 10 ** decimals8;
    }
}