Implement Bigint from implementation for integer types larger than the pointer type

This commit is contained in:
Timothy Warren 2020-09-11 15:23:42 -04:00
parent cf262073dd
commit d90b762754

View File

@ -14,7 +14,7 @@ use alloc::string::*;
use std::prelude::v1::*;
use core::cmp::{Ordering, PartialOrd, PartialEq};
use core::convert::TryInto;
use core::convert::*;
use core::mem::replace;
use core::ops::{
Add, AddAssign, Div, DivAssign, Mul, MulAssign, Neg, Not, Rem, RemAssign, Sub, SubAssign,
@ -465,7 +465,36 @@ macro_rules! impl_from_larger {
impl From<$s> for BigInt {
/// Create a `BigInt` from a signed integer primitive
fn from(n: $s) -> Self {
todo!();
use core::usize::MAX;
let target_radix: $s = (MAX as $s) + 1;
let sign = if n < 0 { Sign::Negative } else { Sign::Positive };
let n = n.abs();
let mut quotient = n / target_radix;
let mut rem = n % target_radix;
if quotient == 0 {
Self::from(rem as usize)
} else {
let mut inner: Vec<usize> = Vec::new();
inner.push(rem as usize);
loop {
rem = quotient % target_radix;
quotient = quotient / target_radix;
inner.push(rem as usize);
if (quotient == 0) {
break;
}
}
BigInt {
inner,
sign,
}
}
}
}
@ -473,14 +502,32 @@ macro_rules! impl_from_larger {
/// Create a `BigInt` from an unsigned integer primitive
fn from(n: $u) -> Self {
use core::usize::MAX;
let target_radix: $u = (MAX as $u) + 1;
let base_usize_value = n / MAX as $u;
let rem = n % MAX as $u;
let mut quotient = n / target_radix;
let mut rem = n % target_radix;
if base_usize_value == 0 {
if quotient == 0 {
Self::from(rem as usize)
} else {
todo!();
let mut inner: Vec<usize> = Vec::new();
inner.push(rem as usize);
loop {
rem = quotient % target_radix;
quotient = quotient / target_radix;
inner.push(rem as usize);
if (quotient == 0) {
break;
}
}
BigInt {
inner,
sign: Sign::Positive
}
}
}
}
@ -536,6 +583,9 @@ impl_ord_literal!(i8,u8,i16,u16,i32,u32,i64,u64,i128,u128);
mod tests {
use super::*;
const RADIX: u128 = core::usize::MAX as u128 + 1;
const I_RADIX: i128 = core::usize::MAX as i128 + 1;
#[test]
fn sanity_checks() {
let int = BigInt::from(45u8);
@ -555,14 +605,14 @@ mod tests {
#[test]
fn test_trim_zeros() {
let mut lotsoftrailing = BigInt {
let mut lots_of_leading = BigInt {
inner: vec![1, 0, 0, 0, 0, 0, 0, 0, 0],
sign: Positive,
};
lotsoftrailing.trim_zeros();
lots_of_leading.trim_zeros();
assert_eq!(BigInt::from(1), lotsoftrailing);
assert_eq!(BigInt::from(1), lots_of_leading);
}
#[test]
@ -815,15 +865,23 @@ mod tests {
}
#[test]
#[should_panic]
fn test_from_large_unsigned() {
BigInt::from(core::u128::MAX);
let big_num: u128 = 9*RADIX + 8;
let res = BigInt::from(big_num);
assert_eq!(res.sign, Sign::Positive, "{:#?}", res);
assert_eq!(res.inner[0], 8usize, "{:#?}", res);
assert_eq!(res.inner[1], 9usize, "{:#?}", res);
}
#[test]
#[should_panic]
fn test_from_large_signed() {
BigInt::from(128i128);
let big_num: i128 = 2*I_RADIX + 3;
let res = BigInt::from(-big_num);
assert_eq!(res.sign, Sign::Negative, "{:#?}", res);
assert_eq!(res.inner[0], 3usize, "{:#?}", res);
assert_eq!(res.inner[1], 2usize, "{:#?}", res);
}
#[test]