Maximum length in the numera system base 10 as usize

This crate offers MaxLenBase10AsUsize trait that is currently implemented for all primitive integers.

According to Rust's reference, primitive numeric integer types in Rust are such:

Numeric types

Integer types

The unsigned integer types consist of:

u8 | 0 | 2⁸-1 u16 | 0 | 2¹⁶-1 u32 | 0 | 2³²-1 u64 | 0 | 2⁶⁴-1 u128 | 0 | 2¹²⁸-1

The signed two's complement integer types consist of:

i8 | -(2⁷) | 2⁷-1 i16 | -(2¹⁵) | 2¹⁵-1 i32 | -(2³¹) | 2³¹-1 i64 | -(2⁶³) | 2⁶³-1 i128 | -(2¹²⁷) | 2¹²⁷-1

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.

Why this trait is needed

In order to allocate (or reserve) memory for storing stringly representations of primitive numeric types efficiently, maximum occupied capacity is needed in order to avoid reallocations and/or unnecessary copying.

Example

You can notice that MaxLenBase10AsUsize is quite long to type and it contains such details as numeral system and the desired type of constant. To make it shorter and more suitable for production code (as opposed to system-level or scientific code), you are advised to rename the imported trait as MaxLen. For clarity, you may also choose to use fully qualified syntax, though it is unnecessary.

  use max_len_base_10_as_usize::MaxLenBase10AsUsize as MaxLen;
  assert_eq!(u8::MAX_LEN_BASE_10_AS_USIZE, <u8 as MaxLen>::MAX_LEN_BASE_10_AS_USIZE);
  assert_eq!(u8::MAX_LEN_BASE_10_AS_USIZE, 3usize);

License