Common Programming Concepts, ch3

Summary:

this chapter introduces essential programming concepts that are common not only in Rust but also in many other languages. The chapter covers variables, data types, functions, comments, and control flow.

key Concepts:

1.Variables and Mutablility

Variables and Mutability:
- Variables are immutable by default in Rust.
- To make a variable mutable, use the mut keyword.

Example:

fn main() {
	
	
	let x = 5; // Immutable variable
	
	let mut y = 6; // Mutable variable

	// x += 1; //Not allowed.
	y += 1; //Allowed because y is mutable

	println!(" result of `y` : {}", y);

}

2. Data Types:

Scalar - integers, floating-point numbers, Booleans and characters.
- int - signed, unsigned : 8 ~ 128 bit and isize, usize.
Compound - tuples, arrays
- Can take user-defined struct and enumeration.

fn main() {
	
	let a: i32 = 10;
	
	let b = 3.14; // Type inference 

	let x : i32 = -1;

	let y : u32 = 1;

	let pi: f64 = 3.14159265359;

	let is_true : bool = true;

	let c : char = 'a';

	//Tuples : can contain mutiple values of different types.
	let person : (i32, f64, &str) = (25, 5.9, "Ho");

	//Arrays : only contains the same type.
	let numbers : [i32, 3] = [3,2,1];
}

3. Functions:

Functions are defined using the fn keyword.
Parameters must have their types explicitly annotated.


fn add(x : i32, y : i32) -> i32 {
	 x + y 
}

fn main() {
	 println!(" x + y = {}", add(3, 5));
}

4. Comments:

Single-line comments start with //
Multi-line comments are rarely used but start with /* and end with */.


fn main() {
	
	// This is a single-line comment

	/* This is a 
		 muti-line comment */

}

5. Control Flow:

if-else, loop, while, and for are available for control flow.

6. Statements and Expressions

Statements: These are instructions that perform some action and do not return a value. They usually end with a semicolon(;).
Expressions : These are pieces of code that evaluate to a value and do not end with a semicolon.
- Expressions can be part of a statement.


fn main() {

		let x = 5; //Statement : This initializes the variable `x` with the value 5.

		let y = (x + 1); // Expression : ` x + 1 ` evaluates to a value (6 in this case).
		
		
		let x1 = 5;  // statement

		let y1 = {
				let z = 3;  // statement
				z + 1 // expression
		}; // this block is also an ??

		println!(" y = {}", y1);


}

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