use core::{cmp, ops};
use crate::{Uint128, Uint256, Uint512, Uint64};
pub trait Isqrt {
#[must_use = "this returns the result of the operation, without modifying the original"]
fn isqrt(self) -> Self;
}
impl<I> Isqrt for I
where
I: Unsigned
+ ops::Add<I, Output = I>
+ ops::Div<I, Output = I>
+ ops::Shr<u32, Output = I>
+ cmp::PartialOrd
+ Copy
+ From<u8>,
{
fn isqrt(self) -> Self {
let mut x0 = self >> 1;
if x0 > 0.into() {
let mut x1 = (x0 + self / x0) >> 1;
while x1 < x0 {
x0 = x1;
x1 = (x0 + self / x0) >> 1;
}
return x0;
}
self
}
}
pub trait Unsigned {}
impl Unsigned for u8 {}
impl Unsigned for u16 {}
impl Unsigned for u32 {}
impl Unsigned for u64 {}
impl Unsigned for u128 {}
impl Unsigned for Uint64 {}
impl Unsigned for Uint128 {}
impl Unsigned for Uint256 {}
impl Unsigned for Uint512 {}
impl Unsigned for usize {}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn isqrt_primitives() {
assert_eq!(0u8.isqrt(), 0);
assert_eq!(1u8.isqrt(), 1);
assert_eq!(24u8.isqrt(), 4);
assert_eq!(25u8.isqrt(), 5);
assert_eq!(26u8.isqrt(), 5);
assert_eq!(36u8.isqrt(), 6);
assert_eq!(26u8.isqrt(), 5);
assert_eq!(26u16.isqrt(), 5);
assert_eq!(26u32.isqrt(), 5);
assert_eq!(26u64.isqrt(), 5);
assert_eq!(26u128.isqrt(), 5);
}
#[test]
fn isqrt_uint64() {
assert_eq!(Uint64::new(24).isqrt(), Uint64::new(4));
}
#[test]
fn isqrt_uint128() {
assert_eq!(Uint128::new(24).isqrt(), Uint128::new(4));
}
#[test]
fn isqrt_uint256() {
assert_eq!(Uint256::from(24u32).isqrt(), Uint256::from(4u32));
assert_eq!(
(Uint256::from(u128::MAX) * Uint256::from(u128::MAX)).isqrt(),
Uint256::try_from("340282366920938463463374607431768211455").unwrap()
);
}
#[test]
fn isqrt_uint512() {
assert_eq!(Uint512::from(24u32).isqrt(), Uint512::from(4u32));
assert_eq!(
(Uint512::from(Uint256::MAX) * Uint512::from(Uint256::MAX)).isqrt(),
Uint512::try_from(
"115792089237316195423570985008687907853269984665640564039457584007913129639935"
)
.unwrap()
);
}
}