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3.data-types.md

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Data-types

  • Implicit definition
let a = 10;
  • Explicit definition
let a:i32 = 10;

Primitive Data types

  • Scalar
    • Numeric
      • Integer
        • Fixed Size Types
          • i8 i16 i32 i64
          • u8 u16 u32 u64
        • Variable Size Types The integer type in which the particular size depends on the underlying machine architecture.
          • isize The pointer-sized signed integer type.
          • usize The pointer-sized unsigned integer type.
      • Float
        • f32 single-precision f64 double-precision floating-point.
    • Non-Numeric
      • Boolean
        • true/false
      • Character
        • let ch:char ='a'; // single quotes
        • let st:&str = "Rust Programming"; // double quotes string is any sequence of characters enclosed within double quotes.
  • Compound
    • Array
      • homogenous sequence of elements
      • By default, arrays are immutable.
      • An array can only be of a fixed length
      • By default, the first element is always at index 0.
      • declare an array let arr:[i32; 4] = [1, 2, 3, 4];
      • Access an element in an array arr[0]
      • making an array mutable let mut arr:[i32;4] = [1, 2, 3, 4];
      • print a full array using debug trait. println!("Array: {:?}", arr);
      • get length of the array. arr.len();
      • Slice is basically a portion of an array.
        • Size of the slice is unknown at compile time.
        • Slice is a two-word object, 1st word is data-pointer & 2nd word is slice length.
        • let _slice:&[i32] = &arr[1..3];
    • Tuple
      • heterogeneous sequences of elements
      • tuples are of fixed length.
      • let data : (&str, &str, i32) = ("Alice", "Lavine", 32);
      • access the value of the tuple data.1
      • making tuples mutable let mut data : (&str, &str, i32) = ("Alice", "Lavine", 32)
      • print tuple println!("Tuple - Data : {:?}", data)
      • getting length of the tuple is not possible, unlike array.len().

Constant Variables

  • const keyword to be used.
  • Constant variables are ones that are declared constant throughout the program scope, meaning, their value cannot be modified.
  • They can be defined in global and local scope.
  • const ID: u32 = 6767;
  • Differences between const and let variables.
    • Scope: const variables can be declared in global and local scope, unlike let variables that are declared only in the local scope.
    • Mutability: const variable cannot be mutable unlike let which can be made mutable using mut keyword.
    • Data-type: Unlike let variables, it is mandatory to define the data type of const variables.
    • Set Value at Runtime: The value of const variable can only be set before running the program whereas the let variable can store the result at runtime.
    • Shadowing: Unlike let variables, const variables cannot be shadowed.