Trait ctf::prelude::ops::Add

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

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

The addition operator +.

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

Examples

Addable points

use std::ops::Add;

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

impl Add for Point {
    type Output = Self;

    fn add(self, other: Self) -> Self {
        Self {
            x: self.x + other.x,
            y: self.y + other.y,
        }
    }
}

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

Implementing Add with generics

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

use std::ops::Add;

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

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

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

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

Required Associated Types

The resulting type after applying the + operator.

Required Methods

Performs the + operation.

Example
assert_eq!(12 + 1, 13);

Implementors

Implements the + operator for concatenating two strings.

This consumes the String on the left-hand side and re-uses its buffer (growing it if necessary). This is done to avoid allocating a new String and copying the entire contents on every operation, which would lead to O(n^2) running time when building an n-byte string by repeated concatenation.

The string on the right-hand side is only borrowed; its contents are copied into the returned String.

Examples

Concatenating two Strings takes the first by value and borrows the second:

let a = String::from("hello");
let b = String::from(" world");
let c = a + &b;
// `a` is moved and can no longer be used here.

If you want to keep using the first String, you can clone it and append to the clone instead:

let a = String::from("hello");
let b = String::from(" world");
let c = a.clone() + &b;
// `a` is still valid here.

Concatenating &str slices can be done by converting the first to a String:

let a = "hello";
let b = " world";
let c = a.to_string() + b;

An addition of Duration to NaiveDate discards the fractional days, rounding to the closest integral number of days towards Duration::zero().

Panics on underflow or overflow. Use NaiveDate::checked_add_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(2014, 1, 2));
assert_eq!(from_ymd(2014, 1, 1) + Duration::days(-1),           from_ymd(2013, 12, 31));
assert_eq!(from_ymd(2014, 1, 1) + Duration::days(364),          from_ymd(2014, 12, 31));
assert_eq!(from_ymd(2014, 1, 1) + Duration::days(365*4 + 1),    from_ymd(2018, 1, 1));
assert_eq!(from_ymd(2014, 1, 1) + Duration::days(365*400 + 97), from_ymd(2414, 1, 1));

An addition of Duration to NaiveDateTime yields another NaiveDateTime.

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_add_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, 8));
assert_eq!(hms(3, 5, 7) + Duration::seconds(-1),        hms(3, 5, 6));
assert_eq!(hms(3, 5, 7) + Duration::seconds(3600 + 60), hms(4, 6, 7));
assert_eq!(hms(3, 5, 7) + Duration::seconds(86_400),
           from_ymd(2016, 7, 9).and_hms(3, 5, 7));
assert_eq!(hms(3, 5, 7) + Duration::days(365),
           from_ymd(2017, 7, 8).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, 980) + Duration::milliseconds(450), hmsm(3, 5, 8, 430));

Leap seconds are handled, but the addition 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(-500), hmsm(3, 5, 59, 800));
assert_eq!(leap + Duration::milliseconds(500),  hmsm(3, 5, 59, 1_800));
assert_eq!(leap + Duration::milliseconds(800),  hmsm(3, 6, 0, 100));
assert_eq!(leap + Duration::seconds(10),        hmsm(3, 6, 9, 300));
assert_eq!(leap + Duration::seconds(-10),       hmsm(3, 5, 50, 300));
assert_eq!(leap + Duration::days(1),
           from_ymd(2016, 7, 9).and_hms_milli(3, 5, 59, 300));

An addition of Duration to NaiveTime wraps around and never overflows or underflows. In particular the addition ignores integral number of days.

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, 8, 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 + 4),         from_hmsm(3, 6, 11, 0));
assert_eq!(from_hmsm(3, 5, 7, 0) + Duration::seconds(7*60*60 - 6*60), from_hmsm(9, 59, 7, 0));
assert_eq!(from_hmsm(3, 5, 7, 0) + Duration::milliseconds(80),        from_hmsm(3, 5, 7, 80));
assert_eq!(from_hmsm(3, 5, 7, 950) + Duration::milliseconds(280),     from_hmsm(3, 5, 8, 230));
assert_eq!(from_hmsm(3, 5, 7, 950) + Duration::milliseconds(-980),    from_hmsm(3, 5, 6, 970));

The addition wraps around.

assert_eq!(from_hmsm(3, 5, 7, 0) + Duration::seconds(22*60*60), from_hmsm(1, 5, 7, 0));
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 addition 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(-500), from_hmsm(3, 5, 59, 800));
assert_eq!(leap + Duration::milliseconds(500),  from_hmsm(3, 5, 59, 1_800));
assert_eq!(leap + Duration::milliseconds(800),  from_hmsm(3, 6, 0, 100));
assert_eq!(leap + Duration::seconds(10),        from_hmsm(3, 6, 9, 300));
assert_eq!(leap + Duration::seconds(-10),       from_hmsm(3, 5, 50, 300));
assert_eq!(leap + Duration::days(1),            from_hmsm(3, 5, 59, 300));

Adds a duration.

Examples

use base::prelude::time::*;
let (secs, subsec_nanos) = (1_566_489_242, 7_000_572);
let mut date = Date::from_timestamp(secs, subsec_nanos);
let duration = SinceStart::parse_secs("7.003000001").unwrap();
date = date + duration;
assert_eq! { date.timestamp(), (secs + 7, subsec_nanos + 3_000_001) }

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