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This chapter explains the basic syntax of Rust language through a HelloWorld example.
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Create a HelloWorld-App folder and navigate to that folder on terminal
C:UsersAdmin>mkdir HelloWorld-App C:UsersAdmin>cd HelloWorld-App C:UsersAdminHelloWorld-App>
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To create a Rust file, execute the following command −
C:UsersAdminHelloWorld-App>notepad Hello.rs
Rust program files have an extension .rs. The above command creates an empty file Hello.rs and opens it in NOTEpad. Add the code given below to this file −
fn
main(){
println!("Rust says Hello to TutorialsPoint !!");
}
The above program defines a function main fn main(). The fn keyword is used to define a function. The main() is a predefined function that acts as an entry point to the program. println! is a predefined macro in Rust. It is used to print a string (here Hello) to the console. Macro calls are always marked with an exclamation mark – !.
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Compile the Hello.rs file using rustc.
C:UsersAdminHelloWorld-App>rustc Hello.rs
Upon successful compilation of the program, an executable file (file_name.exe) is generated. To verify if the .exe file is generated, execute the following command.
C:UsersAdminHelloWorld-App>dir //lists the files in folder Hello.exe Hello.pdb Hello.rs
- Execute the Hello.exe file and verify the output.
What is a macro?
Rust provides a powerful macro system that allows meta-programming. As you have seen in the previous example, macros look like functions, except that their name ends with a bang(!), but instead of generating a function call, macros are expanded into source code that gets compiled with the rest of the program. Therefore, they provide more runtime features to a program unlike functions. Macros are an extended version of functions.
Using the println! Macro – Syntax
println!(); // prints just a newline
println!("hello ");//prints hello
println!("format {} arguments", "some"); //prints format some arguments
Comments in Rust
Comments are a way to improve the readability of a program. Comments can be used to include additional information about a program like author of the code, hints about a function/ construct, etc. The compiler ignores comments.
Rust supports the following types of comments −
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Single-line comments ( // ) − Any text between a // and the end of a line is treated as a comment
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Multi-line comments (/* */) − These comments may span multiple lines.
Example
//this is single line comment /* This is a Multi-line comment */
Execute online
Rust programs can be executed online through Tutorialspoint Coding Ground. Write the HelloWorld program in the Editor tab and click Execute to view result.
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