Trait charts::prelude::alloc::ops::Sub

1.0.0 · source · [−]
pub trait Sub<Rhs = Self> {
    type Output;

    fn sub(self, rhs: Rhs) -> Self::Output;
}
Expand description

The subtraction operator -.

Note that Rhs is Self by default, but this is not mandatory. For example, std::time::SystemTime implements Sub<Duration>, which permits operations of the form SystemTime = SystemTime - Duration.

Examples

Subtractable points

use std::ops::Sub;

#[derive(Debug, Copy, Clone, PartialEq)]
struct Point {
    x: i32,
    y: i32,
}

impl Sub for Point {
    type Output = Self;

    fn sub(self, other: Self) -> Self::Output {
        Self {
            x: self.x - other.x,
            y: self.y - other.y,
        }
    }
}

assert_eq!(Point { x: 3, y: 3 } - Point { x: 2, y: 3 },
           Point { x: 1, y: 0 });

Implementing Sub with generics

Here is an example of the same Point struct implementing the Sub trait using generics.

use std::ops::Sub;

#[derive(Debug, PartialEq)]
struct Point<T> {
    x: T,
    y: T,
}

// Notice that the implementation uses the associated type `Output`.
impl<T: Sub<Output = T>> Sub for Point<T> {
    type Output = Self;

    fn sub(self, other: Self) -> Self::Output {
        Point {
            x: self.x - other.x,
            y: self.y - other.y,
        }
    }
}

assert_eq!(Point { x: 2, y: 3 } - Point { x: 1, y: 0 },
           Point { x: 1, y: 3 });

Required Associated Types

The resulting type after applying the - operator.

Required Methods

Performs the - operation.

Example
assert_eq!(12 - 1, 11);

Implementors

A subtraction of Duration from NaiveDate discards the fractional days, rounding to the closest integral number of days towards Duration::zero(). It is the same as the addition with a negated Duration.

Panics on underflow or overflow. Use NaiveDate::checked_sub_signed to detect that.

Example

use chrono::{Duration, NaiveDate};

let from_ymd = NaiveDate::from_ymd;

assert_eq!(from_ymd(2014, 1, 1) - Duration::zero(),             from_ymd(2014, 1, 1));
assert_eq!(from_ymd(2014, 1, 1) - Duration::seconds(86399),     from_ymd(2014, 1, 1));
assert_eq!(from_ymd(2014, 1, 1) - Duration::seconds(-86399),    from_ymd(2014, 1, 1));
assert_eq!(from_ymd(2014, 1, 1) - Duration::days(1),            from_ymd(2013, 12, 31));
assert_eq!(from_ymd(2014, 1, 1) - Duration::days(-1),           from_ymd(2014, 1, 2));
assert_eq!(from_ymd(2014, 1, 1) - Duration::days(364),          from_ymd(2013, 1, 2));
assert_eq!(from_ymd(2014, 1, 1) - Duration::days(365*4 + 1),    from_ymd(2010, 1, 1));
assert_eq!(from_ymd(2014, 1, 1) - Duration::days(365*400 + 97), from_ymd(1614, 1, 1));

A subtraction of Duration from NaiveDateTime yields another NaiveDateTime. It is the same as the addition with a negated Duration.

As a part of Chrono’s leap second handling, the addition assumes that there is no leap second ever, except when the NaiveDateTime itself represents a leap second in which case the assumption becomes that there is exactly a single leap second ever.

Panics on underflow or overflow. Use NaiveDateTime::checked_sub_signed to detect that.

Example

use chrono::{Duration, NaiveDate};

let from_ymd = NaiveDate::from_ymd;

let d = from_ymd(2016, 7, 8);
let hms = |h, m, s| d.and_hms(h, m, s);
assert_eq!(hms(3, 5, 7) - Duration::zero(),             hms(3, 5, 7));
assert_eq!(hms(3, 5, 7) - Duration::seconds(1),         hms(3, 5, 6));
assert_eq!(hms(3, 5, 7) - Duration::seconds(-1),        hms(3, 5, 8));
assert_eq!(hms(3, 5, 7) - Duration::seconds(3600 + 60), hms(2, 4, 7));
assert_eq!(hms(3, 5, 7) - Duration::seconds(86_400),
           from_ymd(2016, 7, 7).and_hms(3, 5, 7));
assert_eq!(hms(3, 5, 7) - Duration::days(365),
           from_ymd(2015, 7, 9).and_hms(3, 5, 7));

let hmsm = |h, m, s, milli| d.and_hms_milli(h, m, s, milli);
assert_eq!(hmsm(3, 5, 7, 450) - Duration::milliseconds(670), hmsm(3, 5, 6, 780));

Leap seconds are handled, but the subtraction assumes that it is the only leap second happened.

let leap = hmsm(3, 5, 59, 1_300);
assert_eq!(leap - Duration::zero(),            hmsm(3, 5, 59, 1_300));
assert_eq!(leap - Duration::milliseconds(200), hmsm(3, 5, 59, 1_100));
assert_eq!(leap - Duration::milliseconds(500), hmsm(3, 5, 59, 800));
assert_eq!(leap - Duration::seconds(60),       hmsm(3, 5, 0, 300));
assert_eq!(leap - Duration::days(1),
           from_ymd(2016, 7, 7).and_hms_milli(3, 6, 0, 300));

A subtraction of Duration from NaiveTime wraps around and never overflows or underflows. In particular the addition ignores integral number of days. It is the same as the addition with a negated Duration.

As a part of Chrono’s leap second handling, the addition assumes that there is no leap second ever, except when the NaiveTime itself represents a leap second in which case the assumption becomes that there is exactly a single leap second ever.

Example

use chrono::{Duration, NaiveTime};

let from_hmsm = NaiveTime::from_hms_milli;

assert_eq!(from_hmsm(3, 5, 7, 0) - Duration::zero(),                  from_hmsm(3, 5, 7, 0));
assert_eq!(from_hmsm(3, 5, 7, 0) - Duration::seconds(1),              from_hmsm(3, 5, 6, 0));
assert_eq!(from_hmsm(3, 5, 7, 0) - Duration::seconds(60 + 5),         from_hmsm(3, 4, 2, 0));
assert_eq!(from_hmsm(3, 5, 7, 0) - Duration::seconds(2*60*60 + 6*60), from_hmsm(0, 59, 7, 0));
assert_eq!(from_hmsm(3, 5, 7, 0) - Duration::milliseconds(80),        from_hmsm(3, 5, 6, 920));
assert_eq!(from_hmsm(3, 5, 7, 950) - Duration::milliseconds(280),     from_hmsm(3, 5, 7, 670));

The subtraction wraps around.

assert_eq!(from_hmsm(3, 5, 7, 0) - Duration::seconds(8*60*60), from_hmsm(19, 5, 7, 0));
assert_eq!(from_hmsm(3, 5, 7, 0) - Duration::days(800),        from_hmsm(3, 5, 7, 0));

Leap seconds are handled, but the subtraction assumes that it is the only leap second happened.

let leap = from_hmsm(3, 5, 59, 1_300);
assert_eq!(leap - Duration::zero(),            from_hmsm(3, 5, 59, 1_300));
assert_eq!(leap - Duration::milliseconds(200), from_hmsm(3, 5, 59, 1_100));
assert_eq!(leap - Duration::milliseconds(500), from_hmsm(3, 5, 59, 800));
assert_eq!(leap - Duration::seconds(60),       from_hmsm(3, 5, 0, 300));
assert_eq!(leap - Duration::days(1),           from_hmsm(3, 6, 0, 300));

Subtracts another NaiveDate from the current date. Returns a Duration of integral numbers.

This does not overflow or underflow at all, as all possible output fits in the range of Duration.

The implementation is a wrapper around NaiveDate::signed_duration_since.

Example

use chrono::{Duration, NaiveDate};

let from_ymd = NaiveDate::from_ymd;

assert_eq!(from_ymd(2014, 1, 1) - from_ymd(2014, 1, 1), Duration::zero());
assert_eq!(from_ymd(2014, 1, 1) - from_ymd(2013, 12, 31), Duration::days(1));
assert_eq!(from_ymd(2014, 1, 1) - from_ymd(2014, 1, 2), Duration::days(-1));
assert_eq!(from_ymd(2014, 1, 1) - from_ymd(2013, 9, 23), Duration::days(100));
assert_eq!(from_ymd(2014, 1, 1) - from_ymd(2013, 1, 1), Duration::days(365));
assert_eq!(from_ymd(2014, 1, 1) - from_ymd(2010, 1, 1), Duration::days(365*4 + 1));
assert_eq!(from_ymd(2014, 1, 1) - from_ymd(1614, 1, 1), Duration::days(365*400 + 97));

Subtracts another NaiveDateTime from the current date and time. This does not overflow or underflow at all.

As a part of Chrono’s leap second handling, the subtraction assumes that there is no leap second ever, except when any of the NaiveDateTimes themselves represents a leap second in which case the assumption becomes that there are exactly one (or two) leap second(s) ever.

The implementation is a wrapper around NaiveDateTime::signed_duration_since.

Example

use chrono::{Duration, NaiveDate};

let from_ymd = NaiveDate::from_ymd;

let d = from_ymd(2016, 7, 8);
assert_eq!(d.and_hms(3, 5, 7) - d.and_hms(2, 4, 6), Duration::seconds(3600 + 60 + 1));

// July 8 is 190th day in the year 2016
let d0 = from_ymd(2016, 1, 1);
assert_eq!(d.and_hms_milli(0, 7, 6, 500) - d0.and_hms(0, 0, 0),
           Duration::seconds(189 * 86_400 + 7 * 60 + 6) + Duration::milliseconds(500));

Leap seconds are handled, but the subtraction assumes that no other leap seconds happened.

let leap = from_ymd(2015, 6, 30).and_hms_milli(23, 59, 59, 1_500);
assert_eq!(leap - from_ymd(2015, 6, 30).and_hms(23, 0, 0),
           Duration::seconds(3600) + Duration::milliseconds(500));
assert_eq!(from_ymd(2015, 7, 1).and_hms(1, 0, 0) - leap,
           Duration::seconds(3600) - Duration::milliseconds(500));

Subtracts another NaiveTime from the current time. Returns a Duration within +/- 1 day. This does not overflow or underflow at all.

As a part of Chrono’s leap second handling, the subtraction assumes that there is no leap second ever, except when any of the NaiveTimes themselves represents a leap second in which case the assumption becomes that there are exactly one (or two) leap second(s) ever.

The implementation is a wrapper around NaiveTime::signed_duration_since.

Example

use chrono::{Duration, NaiveTime};

let from_hmsm = NaiveTime::from_hms_milli;

assert_eq!(from_hmsm(3, 5, 7, 900) - from_hmsm(3, 5, 7, 900), Duration::zero());
assert_eq!(from_hmsm(3, 5, 7, 900) - from_hmsm(3, 5, 7, 875), Duration::milliseconds(25));
assert_eq!(from_hmsm(3, 5, 7, 900) - from_hmsm(3, 5, 6, 925), Duration::milliseconds(975));
assert_eq!(from_hmsm(3, 5, 7, 900) - from_hmsm(3, 5, 0, 900), Duration::seconds(7));
assert_eq!(from_hmsm(3, 5, 7, 900) - from_hmsm(3, 0, 7, 900), Duration::seconds(5 * 60));
assert_eq!(from_hmsm(3, 5, 7, 900) - from_hmsm(0, 5, 7, 900), Duration::seconds(3 * 3600));
assert_eq!(from_hmsm(3, 5, 7, 900) - from_hmsm(4, 5, 7, 900), Duration::seconds(-3600));
assert_eq!(from_hmsm(3, 5, 7, 900) - from_hmsm(2, 4, 6, 800),
           Duration::seconds(3600 + 60 + 1) + Duration::milliseconds(100));

Leap seconds are handled, but the subtraction assumes that there were no other leap seconds happened.

assert_eq!(from_hmsm(3, 0, 59, 1_000) - from_hmsm(3, 0, 59, 0), Duration::seconds(1));
assert_eq!(from_hmsm(3, 0, 59, 1_500) - from_hmsm(3, 0, 59, 0),
           Duration::milliseconds(1500));
assert_eq!(from_hmsm(3, 0, 59, 1_000) - from_hmsm(3, 0, 0, 0), Duration::seconds(60));
assert_eq!(from_hmsm(3, 0, 0, 0) - from_hmsm(2, 59, 59, 1_000), Duration::seconds(1));
assert_eq!(from_hmsm(3, 0, 59, 1_000) - from_hmsm(2, 59, 59, 1_000),
           Duration::seconds(61));

Subtracts a float directly.

Panics if the provided value is NaN or the computation results in NaN