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// ----------------------------------------------------------------------------
// Copyright: (c) 2021 ff. Michael Amrhein (michael@adrhinum.de)
// License: This program is part of a larger application. For license
// details please read the file LICENSE.TXT provided together
// with the application.
// ----------------------------------------------------------------------------
// $Source: src/round.rs $
// $Revision: 2025-11-28T21:00:03+01:00 $
use fpdec_core::{i128_div_rounded, ten_pow, Round};
use crate::Decimal;
#[cfg(doc)]
use crate::RoundingMode;
impl Round for Decimal {
/// Returns a new `Decimal` with its value rounded to `n_frac_digits`
/// fractional digits according to the current [RoundingMode].
///
/// # Panics
///
/// Panics if the resulting value can not be represented by `Decimal`!
///
/// # Examples
///
/// ```rust
/// # use fpdec::{Dec, Decimal, Round};
/// let d = Dec!(28.27093);
/// let r = d.round(4);
/// assert_eq!(r.to_string(), "28.2709");
/// let r = d.round(1);
/// assert_eq!(r.to_string(), "28.3");
/// let r = d.round(0);
/// assert_eq!(r.to_string(), "28");
/// let r = d.round(-1);
/// assert_eq!(r.to_string(), "30");
/// ```
#[allow(clippy::cast_possible_wrap)]
#[allow(clippy::cast_sign_loss)]
fn round(self, n_frac_digits: i8) -> Self {
if n_frac_digits >= self.n_frac_digits as i8 {
self
} else if n_frac_digits < self.n_frac_digits as i8 - 38 {
Self::ZERO
} else {
// n_frac_digits < self.n_frac_digits
let shift: u8 = (self.n_frac_digits as i8 - n_frac_digits) as u8;
let divisor = ten_pow(shift);
let coeff = i128_div_rounded(self.coeff, divisor, None);
if n_frac_digits >= 0 {
Self {
coeff,
n_frac_digits: n_frac_digits as u8,
}
} else {
// shift back
Self {
coeff: coeff * ten_pow(-n_frac_digits as u8),
n_frac_digits: 0,
}
}
}
}
/// Returns a new `Decimal` instance with its value rounded to
/// `n_frac_digits` fractional digits according to the current
/// [RoundingMode], wrapped in `Option::Some`, or `Option::None` if the
/// result can not be represented by `Decimal`.
///
/// # Examples
///
/// ```rust
/// # use fpdec::{Dec, Decimal, Round};
/// # fn main() {
/// # fn f() -> Option<Decimal> {
/// let d = Dec!(28.27093);
/// let r = d.checked_round(4)?;
/// assert_eq!(r.to_string(), "28.2709");
/// let r = d.checked_round(0)?;
/// assert_eq!(r.to_string(), "28");
/// let d = Dec!(170141183460469231731687303715884105727);
/// let r = d.checked_round(-3);
/// assert!(r.is_none());
/// # Option::None
/// # } f();}
/// ```
#[allow(clippy::cast_possible_wrap)]
#[allow(clippy::cast_sign_loss)]
fn checked_round(self, n_frac_digits: i8) -> Option<Self> {
if n_frac_digits >= self.n_frac_digits as i8 {
Some(self)
} else if n_frac_digits < self.n_frac_digits as i8 - 38 {
Some(Self::ZERO)
} else {
// n_frac_digits < self.n_frac_digits
let shift: u8 = (self.n_frac_digits as i8 - n_frac_digits) as u8;
let divisor = ten_pow(shift);
let coeff = i128_div_rounded(self.coeff, divisor, None);
if n_frac_digits >= 0 {
Some(Self {
coeff,
n_frac_digits: n_frac_digits as u8,
})
} else {
// shift back
coeff.checked_mul(ten_pow(-n_frac_digits as u8)).map(
|coeff| Self {
coeff,
n_frac_digits: 0,
},
)
}
}
}
}
#[cfg(test)]
mod round_decimal_tests {
use super::*;
#[test]
fn test_decimal_round_no_op() {
let x = Decimal::new_raw(12345, 2);
let y = x.round(3);
assert_eq!(x.coefficient(), y.coefficient());
assert_eq!(x.n_frac_digits(), y.n_frac_digits());
let y = x.checked_round(5).unwrap();
assert_eq!(x.coefficient(), y.coefficient());
assert_eq!(x.n_frac_digits(), y.n_frac_digits());
}
#[test]
fn test_decimal_round_result_zero() {
let x = Decimal::new_raw(12345, 2);
let y = x.round(-3);
assert_eq!(y.coefficient(), 0);
assert_eq!(y.n_frac_digits(), 0);
let y = x.round(-37);
assert_eq!(y.coefficient(), 0);
assert_eq!(y.n_frac_digits(), 0);
let y = x.checked_round(-9).unwrap();
assert_eq!(y.coefficient(), 0);
assert_eq!(y.n_frac_digits(), 0);
let y = x.checked_round(-42).unwrap();
assert_eq!(y.coefficient(), 0);
assert_eq!(y.n_frac_digits(), 0);
}
#[test]
fn test_decimal_round() {
let d = Decimal::new_raw(12345, 0);
assert_eq!(d.round(-1).coefficient(), 12340);
let d = Decimal::new_raw(1285, 0);
assert_eq!(d.round(-2).coefficient(), 1300);
let d = Decimal::new_raw(12345, 1);
assert_eq!(d.round(0).coefficient(), 1234);
let d = Decimal::new_raw(1285, 2);
assert_eq!(d.round(0).coefficient(), 13);
let d = Decimal::new_raw(12345678909876543, 7);
assert_eq!(d.round(0).coefficient(), 1234567891);
let d = Decimal::new_raw(123455, 9);
assert_eq!(d.round(8).coefficient(), 12346);
}
#[test]
#[should_panic]
fn test_decimal_round_overflow() {
let d = Decimal::new_raw(0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF, 0);
let _ = d.round(-8);
}
#[test]
fn test_decimal_checked_round() {
let d = Decimal::new_raw(12345, 0);
assert_eq!(d.checked_round(-1).unwrap().coefficient(), 12340);
let d = Decimal::new_raw(1285, 0);
assert_eq!(d.checked_round(-2).unwrap().coefficient(), 1300);
let d = Decimal::new_raw(12345, 1);
assert_eq!(d.checked_round(0).unwrap().coefficient(), 1234);
let d = Decimal::new_raw(1285, 2);
assert_eq!(d.checked_round(0).unwrap().coefficient(), 13);
let d = Decimal::new_raw(12345678909876543, 7);
assert_eq!(d.checked_round(0).unwrap().coefficient(), 1234567891);
let d = Decimal::new_raw(123455, 9);
assert_eq!(d.checked_round(8).unwrap().coefficient(), 12346);
let d =
Decimal::new_raw(0x7FFF_FFFF_FFFF_FFFF_FFFF_FFFF_FFFF_FFFF, 0);
let res = d.checked_round(-1);
assert!(res.is_none());
let d =
Decimal::new_raw(0x7FFF_FFFF_FFFF_FFFF_FFFF_FFFF_FFFF_FFFF, 0);
let res = d.checked_round(-1);
assert!(res.is_none());
}
}