Data types in Rust

• Primitive Types
  • Default types of implicit definition
  • Max size
• Strings
• Tuples
• Arrays
• Vectors

Primitive Types

Integers: i8, u8, i16, u16, i32, u32, i64, u64, i128, u128.

Floats: f32, f64.

Boolean

Character: wrapped by ''

let character = 'a';

Note that

let character2 = "b";

is not a char, it’s a &str instead.

Default types of implicit definition

let a = 1;  // default is i32

let b = 2.5;  // default is f64

Max size

println!("Max i32: {}", std::i32::MAX);

result is:

Max i32: 2147483647

Strings

There are two types of strings in rust

• Immutable, fixed-length strings stored in the stack.
• Growable strings allocated from heap.

Functions they have in common:

• .len(): returns the length
• .contains(): pass in substring, returns if contains it
• .replace(): replace substring
• and many more

What String have in addition:

• .push(): takes in a char, append it to the String
• .push_str(): takes in a immutable string, and append it

Tuples

A collection of data that can have different types.

let person: (&str, &str, i8) = ("3DRX", "Beijing", 20);
println!("{} is from {} and is {} years old.",
         person.0, person.1, person.2);

The result:

3DRX is from Beijing and is 20 years old.

Arrays

A collection of data that have same types, fixed length, stack allocated.

let numbers: [i32; 5] = [1, 2, 3, 4, 5];
println!("{:?}", numbers);
println!("The first number: {:?}.", numbers[0]);

The result:

[1, 2, 3, 4, 5]
The first number: 1.

Note that you have to use {:?} to print an entire tuple or array.

Common functions of array:

• .len(): the length
• To get the size of memory used by an array

  let size_in_bytes: usize = std::mem::size_of_val(&my_array);

Slice of array:

let slice_of_numbers = &numbers[0..2];
println!("The slice: {:?}.", slice_of_numbers);

The output is:

The slice: [1, 2].

Vectors

let num_vec: Vec<i32> = vec![1, 2, 3, 4, 5];

Vectors have all the features of array, and when set to mut, they have .push() and .pop() functions.