Journal

24 Nov 2021

• TIL
  • 1. ERC20 and ERC721 Tokens
  • 2. Overflows & Underflows
  • 3. NatSpec Format
• General

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TIL

I spent this morning’s deep work session working on the cryptozombies courses. I finished creating the app and I’m currently on the last course which deals with creating a basic web page where users can interact with it! Here are my main takeaways so far:

1. ERC20 and ERC721 Tokens

• ERC20 = tokens that act like currency
• ERC721 = tokens that are like collectibles (NFTs)

2. Overflows & Underflows

• uint8 = 2^8 = 256 = max value
• overflow

  uint8 var = 256;
  var = var + 1 // 256 + 1 = 0 due to hitting max value
  

• underflow

  uint8 var = 0;
  var = var - 1 // 0 - 1 = 256 due to hitting min value
  

• best practice is to use the SafeMath library that provides overflow checks and reverts transactions when it occurs

3. NatSpec Format

• Ethereum Natural Language Specification Format
• special form of comments in Solidity contracts that provide rich documentation
• example:

pragma solidity ^0.5.6;

/// @title A simulator for trees
/// @author Larry A. Gardner
/// @notice You can use this contract for only the most basic simulation
/// @dev All function calls are currently implemented without side effects
contract Tree {
    /// @author Mary A. Botanist
    /// @notice Calculate tree age in years, rounded up, for live trees
    /// @dev The Alexandr N. Tetearing algorithm could increase precision
    /// @param rings The number of rings from dendrochronological sample
    /// @return age in years, rounded up for partial years
    function age(uint256 rings) external pure returns (uint256) {
        return rings + 1;
    }
}

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General

I mostly worked on boring persistent volume replication documentation today. I’m in desperate need of a change of pace at work. Thanksgiving is tomorrow! I’m thankful for my career and my relationships. Maybe a four day weekend will be enough to reignite the flame that sizzled out. Have a great weekend!

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