Numeric types

Integer types

The unsigned integer types consist of:

The signed two’s complement integer types consist of:

Floating-point types

The IEEE 754-2008 “binary32” and “binary64” floating-point types are f32 and f64, respectively.

Machine-dependent integer types

The usize type is an unsigned integer type with the same number of bits as the platform’s pointer type. It can represent every memory address in the process.

The isize type is a signed integer type with the same number of bits as the platform’s pointer type. The theoretical upper bound on object and array size is the maximum isize value. This ensures that isize can be used to calculate differences between pointers into an object or array and can address every byte within an object along with one byte past the end.

usize and isize are at least 16-bits wide.

Note: Many pieces of Rust code may assume that pointers, usize, and isize are either 32-bit or 64-bit. As a consequence, 16-bit pointer support is limited and may require explicit care and acknowledgment from a library to support.

Bit validity

For every numeric type, T, the bit validity of T is equivalent to the bit validity of [u8; size_of::<T>()]. An uninitialized byte is not a valid u8.