Primitives
Rust provides access to a wide variety of primitives. A sample includes:
Scalar Types
- signed integers:
i8,i16,i32,i64,i128andisize(pointer size) - unsigned integers:
u8,u16,u32,u64,u128andusize(pointer size) - floating point:
f32,f64 charUnicode scalar values like'a','α'and'∞'(4 bytes each)booleithertrueorfalse- and the unit type
(), whose only possible value is an empty tuple:()
Despite the value of a unit type being a tuple, it is not considered a compound type because it does not contain multiple values.
Compound Types
- arrays like
[1, 2, 3] - tuples like
(1, true)
Variables can always be type annotated. Numbers may additionally be
annotated via a suffix or by default. Integers default to i32 and
floats to f64. Note that Rust can also infer types from context.
fn main() { // Variables can be type annotated. let logical: bool = true; let a_float: f64 = 1.0; // Regular annotation let an_integer = 5i32; // Suffix annotation // Or a default will be used. let default_float = 3.0; // `f64` let default_integer = 7; // `i32` // A type can also be inferred from context let mut inferred_type = 12; // Type i64 is inferred from another line inferred_type = 4294967296i64; // A mutable variable's value can be changed. let mut mutable = 12; // Mutable `i32` mutable = 21; // Error! The type of a variable can't be changed. mutable = true; // Variables can be overwritten with shadowing. let mutable = true; }
See also:
the std library, mut, inference, and shadowing