Solidity programming language: hex string, enum enum

Hexadecimal string

The hexadecimal string hex is not a Solidity data type because you cannot use hex as a type. When hex is added to the front of the literal, its role is to define the data format of the literal, which must be an even-numbered string of [0-9a-fA-F]. This way, when a specific data type is used to reference a hex string, it is implicitly converted. For example, string memory h = hex"010A31", the actual content of the converted string h is \u0001\n1.

In addition, when using a fixed-length byte array of types bytes4, the hex length cannot exceed the actual length of the reference type. For example, bytes4 b = hex "AABBccddee" cannot be compiled.

pragma solidity >=0.4.0 <0.6.0; contract EgHex{ function test() public returns(string memory){ string memory h = hex"010A31"; //string memory h = hex"010G" return h; } function test1() public returns(string memory){ string memory h = hex"010A"; return h; } function test2() public returns(bytes4){ //bytes4 b = hex"AABBccddee"; bytes4 c = hex"AABB"; bytes4 b = hex"AABBccdd"; return b; } function test3() public returns(bytes memory){ bytes memory b = hex"AABBccdd"; return b; } } 

pragma solidity >=0.4.0 <0.6.0; contract EgHex{ function test() public returns(string memory){ string memory h = hex"010A31"; //string memory h = hex"010G" return h; } function test1() public returns(string memory){ string memory h = hex"010A"; return h; } function test2() public returns(bytes4){ //bytes4 b = hex"AABBccddee"; bytes4 c = hex"AABB"; bytes4 b = hex"AABBccdd"; return b; } function test3() public returns(bytes memory){ bytes memory b = hex"AABBccdd"; return b; } }

pragma solidity >=0.4.0 <0.6.0; contract EgHex{ function test() public returns(string memory){ string memory h = hex"010A31"; //string memory h = hex"010G" return h; } function test1() public returns(string memory){ string memory h = hex"010A"; return h; } function test2() public returns(bytes4){ //bytes4 b = hex"AABBccddee"; bytes4 c = hex"AABB"; bytes4 b = hex"AABBccdd"; return b; } function test3() public returns(bytes memory){ bytes memory b = hex"AABBccdd"; return b; } }

pragma solidity >=0.4.0 <0.6.0; contract EgHex{ function test() public returns(string memory){ string memory h = hex"010A31"; //string memory h = hex"010G" return h; } function test1() public returns(string memory){ string memory h = hex"010A"; return h; } function test2() public returns(bytes4){ //bytes4 b = hex"AABBccddee"; bytes4 c = hex"AABB"; bytes4 b = hex"AABBccdd"; return b; } function test3() public returns(bytes memory){ bytes memory b = hex"AABBccdd"; return b; } }

pragma solidity >=0.4.0 <0.6.0; contract EgHex{ function test() public returns(string memory){ string memory h = hex"010A31"; //string memory h = hex"010G" return h; } function test1() public returns(string memory){ string memory h = hex"010A"; return h; } function test2() public returns(bytes4){ //bytes4 b = hex"AABBccddee"; bytes4 c = hex"AABB"; bytes4 b = hex"AABBccdd"; return b; } function test3() public returns(bytes memory){ bytes memory b = hex"AABBccdd"; return b; } }

Enumen enum

Enumeration types in Solidity are basically the same as in other programming languages. Let's look at an example, such as defining a season's enumeration.

Pragma solidity >=0.4.0 <0.6.0;

 contract EgEnum{ enum Season{Spring, Summer, Autumn, Winter} 

Function printSeason(Season s) public returns(Season) { return s; }

Function test1() public returns(Season){ return printSeason(Season.Spring); }

Function test2() public returns(uint){ uint s = uint(Season.Spring); return s; }

Function test3() public returns(Season){ //Season s = Season(5);//Boundary Season s = Season(3); return s; } }

  1. The actual type of enum is an unsigned integer. When the number of enumerations is in the range of 0-127, then enum is of type uint8. If it is in the range of 0-32,767, then enum is uint16 type, and so on.
  2. Since enum is a uint type, you can do type conversion. For example, uint s = uint(Season.Spring) converts the enumeration of the Season type to uint, and of course you can convert it to uint8, as long as it does not cross the boundary. Similarly, Season s = Season(3) converts uint to Season type. Also note that the integer does not exceed the range of the enumeration. For example, Season's range is 0-3. If you convert 5 to Season, you will run an exception and the compiler will pass.

Author: thank HPB technology community organize feeds.

Wang Xiaoming blog http://wangxiaoming.com/

Wang Xiaoming: Founder of HPB core chain, Babbitt columnist. More than ten years of experience in financial big data and blockchain technology development, he has participated in the creation of UnionPay big data. The main creative blockchain teaching video program "Ming Shuo" more than 30 issues, compiled the "Ethernet official website document Chinese version", and as the main author wrote the "blockchain development guide", in the Chinese blockchain community with ID "blue lotus "famous.

We will continue to update Blocking; if you have any questions or suggestions, please contact us!

Share:

Was this article helpful?

93 out of 132 found this helpful

Discover more

Blockchain

Blockchain data analysis lets you see the counterparties

By analyzing the blockchain data set, we will have a better and clearer understanding of cryptocurrencies. (Image sou...

Blockchain

Clear out while the time is right? FTX and Alameda-related addresses recently transferred $30 million worth of assets.

In September, FTX was approved for liquidation and has been frequently withdrawing large amounts of assets in the pas...

Policy

🚀 FTX Claims Reach for the Sky: AI Investments Boost Recovery Potential

FTX's investment in AI companies has significantly increased their potential recovery during their bankruptcy procedu...

Opinion

Bloomberg Thousands of Words Uncover How SBF's Elite Parents Helped Him Build a Cryptocurrency Empire?

A tall building rises from flat ground, and the success of FTX is not the result of one person's efforts. With the ba...

Blockchain

Babbitt column | Case study: Exchange "downtime", does the holder lose any compensation?

Source of this article: Xiao Sa Author: Tan Hao Guo Xiao Sa The currency circle trading platform advertises that &quo...