Rust basics

The rust's syntax

So in every Programming language all programs have at starting point , it varies from each language . In rust it stars with function main(). It marks the starting point of every rust code . So in whatever rust code we can see this function main. So the most basic program in every language is printing "Hello world" . So let's do it

fn main() {
    println!("Hello world");
}

here as we can see we started from " fn main() " which indicates the starting point . The keyword println! is used to print anything inside the parenthesis with double quotation .

Now let's assign a value to an variable

So for assigning an value to a variable , we have to use an keyword named 'let' . So this keyword allows us to assign a value to a variable .

fn main () {
    let x = 23 ; // <- This double slash in rust means it is an comment.
                // Rust doesn't care about anything behind these slashes. 
                // the semicolon after 23 is very essential as it marks the
                // end of an statement else an error will pop up
}

So here we assign the value x to 23 .

Printing the value of a assigned variable

Now we have seen about assigning a value to a variable . Now let's see how to print a variable.

fn main() {
    let x: i32 = 46 ;
    println!("The value of x is : {} " , x );
    //                            ^^^   ^^^
    // The curly braces is were the value of the varible after the 
    // comma is printed
}

Here we assign a value 46 to the variable x. The : i32 after x tells the compiler it is an integer . It isn't necessary , there are also other integer types like i8 , i16 , i64 according to the no of bits and bytes they take.

Mutability of variable

A mutable variable means it's value can be changed again . But a an immutable variables value cannot change if assigned .

fn main() {
    let mut x = 23; // Rust's variables are immutable in default 
    // ^^^^ The 'mut' is the keyword for making a mutable variable    
    println!("X is {} ", x);
    x = 34 ;// Mutable variable 
    println!("X is {} ", x);
}

Exercise : 1. Print a string with an output : Rust is amazing .

2. Assign a value to a variable and print it .

1. Make a mutable variable print it and change it's value and try printing it.

2. Note :

   Please kindly check the previous Rust Basics article series for updates now an then.