Trait ilog::IntLog

source · 
pub trait IntLog {
    fn log10(self) -> usize;
    fn log2(self) -> usize;
    fn checked_log10(self) -> Option<usize>;
    fn checked_log2(self) -> Option<usize>;
}
Expand description

Trait that provides logarithms for integer types.

The log2 and log10 methods are optimized for the integer width and are [inline] since the code remains small enough. They typically use constant tables that are only stored once, even if the methods using them are inlined multiple times.

The checked versions of the methods, checked_log2 and checked_log10, return None if the logarithm is undefined for the parameter value, whereas the unchecked methods mentioned above simply panic or return a wrong value.

Required Methods§

Returns the largest integer less than or equal to the base 10 logarithm of the integer.

Logarithms are only defined on positive values, calling log10 with a null or a negative argument may trigger a panic or return a wrong value. See checked_log10 for a method that checks its argument first.

Examples
let value: u64 = 100;
assert_eq!(value.log10(), 2);
assert_eq!(i32::log10(99), 1);

Returns the largest integer less than or equal to the base 2 logarithm of the integer.

Logarithms are only defined on positive values, calling log10 with a null or a negative argument may trigger a panic or return a wrong value. See checked_log2 for a method that checks its argument first.

Examples
let value: u64 = 64;
assert_eq!(value.log2(), 6);
assert_eq!(i32::log2(63), 5);

Checked base 10 logarithm. Returns the largest integer less than or equal to the base 10 logarithm of the integer, or None if it doesn’t exist.

Examples
assert_eq!(100_u32.checked_log10(), Some(2));
assert_eq!(u64::checked_log10(99), Some(1));
assert_eq!(0_u32.checked_log10(), None);

Checked base 10 logarithm. Returns the largest integer less than or equal to the base 10 logarithm of the integer, or None if it doesn’t exist.

Examples
assert_eq!(64_u32.checked_log2(), Some(6));
assert_eq!(u64::checked_log2(63), Some(5));
assert_eq!(0_u32.checked_log2(), None);

Implementations on Foreign Types§

Implementors§