Variables, Constants, and Data Types
In Rust, variables are declared using the let keyword. All variables are immutable by default, which means once a value is bound to a variable, it cannot be changed. If you want to make a variable mutable, the mut keyword is used. May - 25/2025Comments, print and format!
a. Comments
Example:
fn main () {
// line;
/*
block;
*/
}
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b. Print
Example:
fn main () {
// No break line!
print!("Hello, world!");
//break line!
println!("Hello, Maria!");
println!("Hello, Carlos!");
}
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c. line break: \n
Example:
fn main () {
// line break: \n
println!("What is your name?\nMy name is Rodolfo!");
// : \n
println!("What is your name?\\nMy name is Rodolfo!");
}
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d. format!
Example:
fn main () {
format!("Hello"); // => "Hello"
format!("Hello, {}!", "world"); // => "Hello, world!"
format!("The number is {}", 1); // => "The number is 1"
format!("{:?}", (3, 4)); // => "(3, 4)"
format!("{value}", value = 4); // => "4"
let people = "Rustaceans";
format!("Hello {people}!"); // => "Hello Rustaceans!"
format!("{} {}", 1, 2); // => "1 2"
format!("{:04}", 42); // => "0042" with leading zeros
format!("{:#?}", (100, 200)); // => "(
// 100,
// 200,
// )"
}
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