[−][src]Trait num_integer::Roots

```pub trait Roots: Integer {
fn nth_root(&self, n: u32) -> Self;

fn sqrt(&self) -> Self { ... }
fn cbrt(&self) -> Self { ... }
}```

Provides methods to compute an integer's square root, cube root, and arbitrary `n`th root.

Required methods

`fn nth_root(&self, n: u32) -> Self`

Returns the truncated principal `n`th root of an integer -- `if x >= 0 { ⌊ⁿ√x⌋ } else { ⌈ⁿ√x⌉ }`

This is solving for `r` in `rⁿ = x`, rounding toward zero. If `x` is positive, the result will satisfy `rⁿ ≤ x < (r+1)ⁿ`. If `x` is negative and `n` is odd, then `(r-1)ⁿ < x ≤ rⁿ`.

Panics

Panics if `n` is zero:

`println!("can't compute ⁰√x : {}", 123.nth_root(0));`

or if `n` is even and `self` is negative:

`println!("no imaginary numbers... {}", (-1).nth_root(10));`

Examples

```use num_integer::Roots;

let x: i32 = 12345;
assert_eq!(x.nth_root(1), x);
assert_eq!(x.nth_root(2), x.sqrt());
assert_eq!(x.nth_root(3), x.cbrt());
assert_eq!(x.nth_root(4), 10);
assert_eq!(x.nth_root(13), 2);
assert_eq!(x.nth_root(14), 1);
assert_eq!(x.nth_root(std::u32::MAX), 1);

assert_eq!(std::i32::MAX.nth_root(30), 2);
assert_eq!(std::i32::MAX.nth_root(31), 1);
assert_eq!(std::i32::MIN.nth_root(31), -2);
assert_eq!((std::i32::MIN + 1).nth_root(31), -1);

assert_eq!(std::u32::MAX.nth_root(31), 2);
assert_eq!(std::u32::MAX.nth_root(32), 1);```

Provided methods

`fn sqrt(&self) -> Self`

Returns the truncated principal square root of an integer -- `⌊√x⌋`

This is solving for `r` in `r² = x`, rounding toward zero. The result will satisfy `r² ≤ x < (r+1)²`.

Panics

Panics if `self` is less than zero:

`println!("no imaginary numbers... {}", (-1).sqrt());`

Examples

```use num_integer::Roots;

let x: i32 = 12345;
assert_eq!((x * x).sqrt(), x);
assert_eq!((x * x + 1).sqrt(), x);
assert_eq!((x * x - 1).sqrt(), x - 1);```

`fn cbrt(&self) -> Self`

Returns the truncated principal cube root of an integer -- `if x >= 0 { ⌊∛x⌋ } else { ⌈∛x⌉ }`

This is solving for `r` in `r³ = x`, rounding toward zero. If `x` is positive, the result will satisfy `r³ ≤ x < (r+1)³`. If `x` is negative, then `(r-1)³ < x ≤ r³`.

Examples

```use num_integer::Roots;

let x: i32 = 1234;
assert_eq!((x * x * x).cbrt(), x);
assert_eq!((x * x * x + 1).cbrt(), x);
assert_eq!((x * x * x - 1).cbrt(), x - 1);

assert_eq!((-(x * x * x)).cbrt(), -x);
assert_eq!((-(x * x * x + 1)).cbrt(), -x);
assert_eq!((-(x * x * x - 1)).cbrt(), -(x - 1));```