Pattern matching in RUST

Pattern matching in RUST

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Pattern matching is a mechanism for checking a value against a pattern. A successful match can also deconstruct a value into its constituent parts. It is a more powerful version of the statementswitch in languages like C++, and Java, it can likewise be used in place of a series of if/else statements.

In Rust, Patterns are a special type of syntax for matching against the structure of types, both complex and simple. Using patterns in conjunction with expressions and match construct gives you more control over a program’s control flow. A pattern consists of a combination of the following:

• Literals
• Destructured arrays, enums, structs, or tuples
• Variables
• Wildcards
• Placeholders

These components describe the shape of the data we’re working with, which we then match against values to determine whether our program has the correct data to continue running a particular piece of code.

1. Pattern matching on Literals, variable and wildcards

fn main() {
let x = 1;
match x {    
    1 => println!("one"),
    2 => println!("two"),
    3 => println!("three"),
    _ => println!("anything"),}
}

2. Pattern matching on Enums and Struct

struct Point {
 x: i32,
 y: i32,
}


fn main() { 
   let p = Point { x: 0, y: 7 };   
   match p { 
      Point { x, y: 0 } => println!("On the x axis at {}", x),
      Point { x: 0, y } => println!("On the y axis at {}", y),
      Point { x, y } => println!("On neither axis: ({}, {})", x, y), 
   }
}

enum Message {
    Quit,
    Move { x: i32, y: i32 },
    Write(String),
    ChangeColor(i32, i32, i32),
}

fn main() {
    let msg = Message::ChangeColor(0, 160, 255);

match msg {
    Message::Quit => {
        println!("The Quit variant has no data to destructure.")    
    },
    Message::Move { x, y } => {
        println!("Move in the x direction {} and in the y direction {}", x,y);    } 
    Message::Write(text) => println!("Text message: {}", text),
    Message::ChangeColor(r, g, b) => { 
        println!("Change the color to red {}, green {}, and blue }", r, g, b )
     }
   }
}

3.Pattern matching on Multiple Possibilities and Pattern Guard

let num = Some(4);
match num {
    Some(x) if x < 5 => println!("less than five: {}",x),
    Some(x) => println("{}",x),
    None  => (), 
}

fn main() {
let x = 4;
let y = false;
match x {
    4 | 5 | 6 if y => println!("yes"),
    _ => println!("no"),
   }
}