Rust - Basic

[NicolaBernini]

Overview

Some Basic Elements about Rust Programming

[NicolaBernini]

Functions

Functions Syntax

• Starts with fn keyword
• Follows the following structure

fn func_name(arg: type, ...) -> type 
{...}

Example

fn square(num: i32) -> i32 
{
    return num*num; 
}

[NicolaBernini]

Variables

• Rust is a statically type language which means the type of each variable is known at compile time

• There are 2 ways to define variable type

  1. Explicitely annotate a variable, using the type annotation syntax as follows

     let var_name: type

  2. Letting the compiler infer it (like C++11 auto)

• Variables are by default immutable but can be made mutable by adding mut specifier in their declaration before their name

let mut var_name: type

• In order to be used variables need to be
  1. Declared, hence the following aspects need to be specified
     • name
     • immutable / mutable category
     • type (explicitly or implicitly)
  2. Initialized, so they need a value attached to them
     • uninitialized variables can not be used in computation

Examples

Immutable Variable explicitly annotated but uninitialized (not usable)

let temp: i32; 

Immutable Variable explicitly annotated and initialization (usable)

let temp: i32 = 56; 

Two stage declaration + initialization equivalent to the above one

let temp: i32; 
temp = 56; 

Immutable Variable with implicitly deducted type as a result of initialization (usable)

let temp = 32; 

Mutable Variable uninitialized

let mut temp: i32; 

Mutable Variable initialized

let mut temp: i32 = 56;