Value Types: Uint, Int, Bool and Enums

Table of Contents

Solidity Value Types

Value types are types where variables store their data directly in memory. When used in function arguments or assignments, the value of these variables is always copied. This means any changes made to the copied variable do not affect the original variable.

Let’s look at a few important types

contract Example {
  uint a;
  int b;
  bool c;

  enum Choice { Up, Down, Left, Right }
  Choice choice = Choice.Up;
}

A contract is similar to a class in object-oriented programming languages like Java, C++, or Python

Unsigned Integer

A non-negative whole numbers

contract Example {
  // uint can be declared in steps of 8
  // where the number represents the number of bits
  uint8 a; // 0 -> 255
  uint16 b; // 0 -> 65535
  uint32 c; // 0 -> 4294967295
  uint64 d; // 0 -> 18446744073709551615
  uint128 e; // 0 -> 340282366920938463463374607431768211455
  uint256 f; // 0 -> 115792089237316195423570985008687907853269984665640564039457584007913129639935

  // uint is an alias for uint256
  uint z1;
  uint256 z2;
}

Signed Integer

A number that could be either positive or negative

contract Example {
  // uint can be declared in steps of 8
  // where the number represents the number of bits
  int8 a; // -128 -> 127
  int16 b; // -32768 -> 32767
  int32 c; // -2147483648 -> 2147483647
  int64 d; // -9223372036854775808 -> 9223372036854775807
  int128 e; // -170141183460469231731687303715884105728 -> 170141183460469231731687303715884105727
  int256 f; // -57896044618658097711785492504343953926634992332820282019728792003956564819968 -> 57896044618658097711785492504343953926634992332820282019728792003956564819967

  // int is an alias for int256
  int z1;
  int256 z2;
}

Boolean

Either true or false

import "forge-std/console.sol";

contract Example {
  constructor(bool myCondition) {
    if(myCondition) {
      // will log yay if myCondition is true
      console.log("yay!");
    }
  }
}

Constructor is a function that runs once upon deployment

Enums

Defining options for a value by name

import "forge-std/console.sol";

contract Example {
  enum Choice { Up, Down, Left, Right }

  constructor(Choice choice) {
    if(choice == Choice.Up) {
      console.log("up");
    }
    if(choice == Choice.Down) {
      console.log("down");
    }
  }
}

Hands-on

learn-solidity-presentations\1a-value-types\examples\0-example-value-types\src\Example.sol

// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.20;

import "forge-std/console.sol";

contract Example {
    uint8 a = 255; // 0 -> 255
    uint256 b = 22; // alias: uint

    int8 c = 127; // -128 -> 127
    int256 d = -55; // alias: int

    bool myCondition = true;
    bool myCondition2; // default value is false

    enum Choice {
        Up,
        Down,
        Left,
        Right
    }

    Choice choice = Choice.Up;

    constructor() {
        console.logUint(type(uint8).min);
        console.logUint(type(uint8).max);

        console.logInt(type(int8).min);
        console.logInt(type(int8).max);

        if (myCondition) {
            console.log("yay");
        }

        if (choice == Choice.Up) {
            console.log("up");
        }
        if (choice == Choice.Down) {
            console.log("down");
        }
        if (choice == Choice.Right) {
            console.log("right");
        }
        if (choice == Choice.Left) {
            console.log("left");
        }
    }
}

edo@DESKTOP-4POSOVK:/mnt/e/Programming/Solidity/learn-solidity-presentations/1a-value-types/examples/0-example-value-types$ forge test -vv
[⠰] Compiling...
No files changed, compilation skipped

Ran 1 test for test/Example.t.sol:ExampleTest
[PASS] testExample() (gas: 187)
Logs:
  0
  255
  -128
  127
  yay
  up

Suite result: ok. 1 passed; 0 failed; 0 skipped; finished in 20.89ms (180.10µs CPU time)

Ran 1 test suite in 91.14ms (20.89ms CPU time): 1 tests passed, 0 failed, 0 skipped (1 total tests)

Learn Solidity. Alchemy University.
Accessed October 7, 2024
https://university.alchemy.com/overview/solidity