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Summary - Data types

Combine different types to build a grade-calculating program.

Data types summary

Scalar types: integers (i8…i128, u8…u128, isize/usize), decimals (f32, f64), bool and char (4-byte Unicode). Compound types: tuples (T1, T2) and arrays [T; N]. Conversions between types are explicit with as; for overflow there are the checked_*/wrapping_*/saturating_* methods.

Safe conversion

as truncates silently; to check whether a value fits, use TryFrom:

let buyuk: i32 = 300;
match u8::try_from(buyuk) {
    Ok(v) => println!("sığdı: {v}"),
    Err(e) => println!("sığmadı: {e}"),
}

For lossless conversions there are From/into: let x: i64 = 5_i32.into();.

Practice Conversion comparison

For let n: i32 = 300;, print the result of n as u8 and of u8::try_from(n).is_err() with println!("{} {}", ...).

Starter code

main.rs
fn main() {
    // buraya yaz
}

Sample solution

main.rs
fn main() {
    let n: i32 = 300;
    println!("{} {}", n as u8, u8::try_from(n).is_err());
}

Expected output

44 true

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 What is <code>300 as u8</code>?

  • 44 Correct answer
  • 255
  • A compile error
  • 300

Explanation: as truncates the high bits in an integer conversion: 300 - 256 = 44. For a safe conversion, u8::try_from(300) returns an error.

2 Lossless conversion

Question 
let kucuk: i32 = 5;
let buyuk: i64 = kucuk.____();
Answer 
let kucuk: i32 = 5;
let buyuk: i64 = kucuk.into();

Explanation: into converts losslessly between types that implement From.

3 Group summary

Term Meaning
i32 / f64 Default number types
char 4-byte Unicode
(T1, T2) Tuple
[T; N] Fixed-length array

All lessons in Beginner

1 Rust basics

  1. What is Rust?
  2. Project with Cargo
  3. Your first program
  4. println! and formatting
  5. Comments
  6. Summary - Rust basics

2 Variables

  1. Variables with let
  2. Mutability with mut
  3. Constants with const
  4. Static variables
  5. Shadowing
  6. Summary - Variables

3 Data types

  1. Integers
  2. Floating point
  3. Bool and char
  4. Tuple
  5. Array
  6. Summary - Data types

4 Strings

  1. &str vs String
  2. Creating a String
  3. Concatenating strings
  4. format! macro
  5. String length
  6. Summary - Strings

5 Project: Calculator

  1. Project skeleton
  2. Reading input
  3. Computing
  4. Error handling
  5. Loop and exit

6 Functions

  1. Defining with fn
  2. Parameters
  3. Return value
  4. Expressions and statements
  5. Early return
  6. Summary - Functions

7 Control flow

  1. if-else
  2. match basics
  3. loop
  4. while loop
  5. for loop
  6. Summary - Control flow

8 Ownership

  1. What is ownership?
  2. Move semantics
  3. Copy trait
  4. Functions and ownership
  5. Return and ownership
  6. Summary - Ownership

9 Borrowing

  1. References
  2. Mutable reference
  3. Borrowing rules
  4. Dangling reference
  5. References and functions
  6. Summary - Borrowing

10 Slices

  1. String slices
  2. Slice syntax
  3. Array slices
  4. Slices and functions
  5. Range types
  6. Summary - Slices

11 Project: Guessing game

  1. Game skeleton
  2. Reading input
  3. Comparing numbers
  4. Random number
  5. Loop and exit

12 Structs

  1. Struct definition
  2. Creating an instance
  3. Tuple struct
  4. Unit-like struct
  5. Field update
  6. Summary - Structs

13 Methods

  1. impl block
  2. self parameter
  3. &mut self
  4. Associated functions
  5. Multiple impl blocks
  6. Summary - Methods

14 Enums

  1. Enum definition
  2. Variants
  3. Variants with data
  4. Option<T>
  5. Option instead of null
  6. Summary - Enums

15 Pattern matching

  1. match patterns
  2. Value binding
  3. if let
  4. while let
  5. _ wildcard
  6. Summary - Pattern matching

16 Project: To-do CLI

  1. Task model
  2. Adding
  3. Listing
  4. Marking done
  5. Reading commands

17 Vectors

  1. Vec<T>
  2. Push and pop
  3. Index and get
  4. Looping a vector
  5. with_capacity
  6. Summary - Vectors

18 Advanced strings

  1. String and &str conversion
  2. chars and bytes
  3. Slicing strings
  4. contains and replace
  5. split and join
  6. Summary - Advanced strings

19 Error handling

  1. Result<T, E>
  2. panic!
  3. ? operator
  4. match and Result
  5. unwrap and expect
  6. Summary - Error handling

20 Beginner final

  1. Vowel counter
  2. Average calculator
  3. Bank account
  4. Temperature converter