count-digits

A no_std trait to count the digits of integer types in various number bases.

Compatible with all primitive integer types and all non-zero integer types.

Examples

use count_digits::CountDigits;

assert_eq!(16, 0b1111000000001101.count_bits());
assert_eq!(16, 0b1111000000001101.count_digits_radix(2_u32));

assert_eq!(06, 0o170015.count_octal_digits());
assert_eq!(06, 0o170015.count_digits_radix(8_u32));

assert_eq!(05, 61453.count_digits());
assert_eq!(05, 61453.count_digits_radix(10_u32));

assert_eq!(04, 0xF00D.count_hex_digits());
assert_eq!(04, 0xF00D.count_digits_radix(16_u32));

[!NOTE] The base-10 functions count_digits() and count_digits_radix(10) do not include the negative sign in their counts.

assert_eq!(5, 12345_i32.wrapping_neg().count_digits());
assert_eq!(5, 12345_i32.wrapping_neg().count_digits_radix(10));

[!NOTE] Negative numbers counted in base-10 are counted differently than negative numbers counted in other number bases.

Since negative numbers represented in base-10 are displayed with a negative sign, the base-10 digit count of a positive number will be equal to the base-10 digit count of the number's negated value, assuming no wrapping occurred.

assert_eq!(
    867_5309_i32.count_digits(),
    867_5309_i32.wrapping_neg().count_digits(),
);

However, the digit counts of negative numbers represented in other bases reflect the twos-complement representation, and the digit count of a positive number will not be the same as the count of its negated value.

assert_ne!(
    0xBAD_i32.count_bits(),
    0xBAD_i32.wrapping_neg().count_bits(),
);
assert_ne!(
    0xBAD_i32.count_octal_digits(),
    0xBAD_i32.wrapping_neg().count_octal_digits(),
);
assert_ne!(
    0xBAD_i32.count_hex_digits(),
    0xBAD_i32.wrapping_neg().count_hex_digits(),
);

for radix in 2..=16 {
    match radix {
        10 => assert_eq!(
            0xF00D_i32.count_digits_radix(radix),
            0xF00D_i32.wrapping_neg().count_digits_radix(radix),
        ),
        _ => assert_ne!(
            0xBAD_i32.count_digits_radix(radix),
            0xBAD_i32.wrapping_neg().count_digits_radix(radix),
        ),
    }
}

This behavior is consistent with Rust's display format.

assert_eq!(1, format!("{:b}",  1_i8).chars().count());
assert_eq!(1, format!("{:o}",  1_i8).chars().count());
assert_eq!(1, format!("{  }",  1_i8).chars().count());
assert_eq!(1, format!("{:x}",  1_i8).chars().count());

assert_eq!(8, format!("{:b}", -1_i8).chars().count());
assert_eq!(3, format!("{:o}", -1_i8).chars().count());
assert_eq!(1, format!("{  }", -1_i8).strip_prefix('-').unwrap().chars().count());
assert_eq!(2, format!("{:x}", -1_i8).chars().count());

Benchmarks

License: MIT

count-digits 0.3.0

count-digits

Examples

Benchmarks