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TIL RUST #4: Scalar and Compound types

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Scalar and Compound types

In Rust, types are classified as scalar or compound based on whether they represent a single value or a collection of values. Scalar types represent single values:

  • signed integers
  • unsigned integers
  • floating point
  • char
  • bool
  • unit type

Note: Although the value of the unit type is a tuple, it is not considered a compound type as it does not contain multiple values.

Compound types represent a collection of values:

  • tuples
  • arrays
  • slices
  • structs
  • enums

Suffix annotation

In Rust, numbers can also be annotated with their type through suffix annotation.

Example:

//normal type annotation
let a: i64 = 23


//suffix annotation
let a = 23i64

Also, unless explicitly mentioned, integers default to i32 and floats to f64.

The Rust compiler modes

rustc itself does the frontend and mid-end of compilation, producing the MIR (Mid-level Intermediate Representation), and then lowers MIR to LLVM-IR. From there, the LLVM backend takes the LLVM-IR and compiles it down to machine code for the target architecture.

Additional (not so important) note

Underscores can be inserted in numeric literals to improve readability, e.g. 1_000 is the same as 1000, and 0.000_001 is the same as 0.000001.