Syntax of Rust

Function goes first

• Similar to C and C++, there must be a main function as the entry point of the program.

• Use fn to declare a function, so concise.

• Use () for receiving parameters, and {} for the actual logic inside the function.

• Remember to use ; to end a statement. As I said, it’s similar to C and C++.

• Example:

Define variables

• You must use let to create a variable.
• let myVar = 3;
• let myVar: u32 = 3; → Explicitly specifies the type of the variable myVar as u32. u32 is a 32-bit unsigned integer type in Rust.
• let mut myVar = 3; → Creates a mutable variable.

• What? Mutable?
• Variables in Rust are immutable by default.(Its value is determined after compilation.)
• It's important to understand that in Rust, some_variable = some_value is not just assigning a value, but rather binding the value to the variable.
• This topic is related to Rust’s Ownership feature, which we will discuss in the next post.
• Here's an example:

• If you understand that variables are bound to values, it becomes easier to grasp variable destructuring:
• Basically, destructuring means extracting values from patterns.

• You can also use const to define a constant value:
• const MY_CONST_VALUE: i32 = 5;
• Constants must always have a type annotation, unlike regular variables.

Statement and expression

• In short:

• Interesting facts:
• In let x = 1;
• x is an expression
• 1 is an expression
• let x = 1; is a statement
• Bound

• Lastly, if an expression doesn’t return anything, it returns ()
• () is both a type and a value, and the value is ().
• You can treat the () as a (), yes, that is it.