00_Cairo Program Entry

Jul 4, 2023121

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This post is translated from Chinese into English through AI.View Original

AI-generated summary

This article discusses the entry point for Cairo programs. It explains that the main function is the entry point for single-file Cairo programs, similar to other programming languages. The article also mentions that the Cairo compiler version used is 2.0.0-rc0 and that the syntax may vary in different versions. It provides an example of a main function that prints a constant value and another example with a return value. Additionally, it briefly mentions the entry point for Starknet smart contracts using the #[starknet::contract] annotation.

00_Cairo Program Entry#

The version of the Cairo compiler used in this article is 2.0.0-rc0. Because Cairo is being updated rapidly, the syntax may vary slightly in different versions, and the content of the article will be updated to the stable version in the future.

Single File Cairo Program Entry#

Similar to most programming languages, the entry point for a single file Cairo program is the main function.

use debug::PrintTrait;

const ONE_HOUR_IN_SECONDS: felt252 = 3600;

fn main(){
    ONE_HOUR_IN_SECONDS.print();
}

Run the command:

cairo-run $file_path

The main function can have a return value, as follows:

fn main() -> felt252 {
   return 10; 
}

The return value will be output in square brackets on this line:

Run completed successfully, returning [10]

Starknet Smart Contract Entry#

Start with #[starknet::contract], and add the contract name after the mod keyword.

#[starknet::contract]
mod ERC20 {
	...
}