Trait Step 

pub trait Step:
    Clone
    + PartialOrd
    + MinMax
    + Sized {
    // Required methods
    fn steps_between(start: &Self, end: &Self) -> (usize, Option<usize>);
    fn forward_checked(start: Self, count: usize) -> Option<Self>;
    fn backward_checked(start: Self, count: usize) -> Option<Self>;

    // Provided methods
    fn forward(start: Self, count: usize) -> Self { ... }
    fn backward(start: Self, count: usize) -> Self { ... }
}

A copy of the unstable std::iter::Step trait required for the iter derive.

Required Methods

fn steps_between(start: &Self, end: &Self) -> (usize, Option<usize>)

Returns the bounds on the number of successor steps required to get from start to end like Iterator::size_hint().

Returns (usize::MAX, None) if the number of steps would overflow usize, or is infinite.

Invariants

For any a, b, and n:

• steps_between(&a, &b) == (n, Some(n)) if and only if Step::forward_checked(&a, n) == Some(b)
• steps_between(&a, &b) == (n, Some(n)) if and only if Step::backward_checked(&b, n) == Some(a)
• steps_between(&a, &b) == (n, Some(n)) only if a <= b
  • Corollary: steps_between(&a, &b) == (0, Some(0)) if and only if a == b
• steps_between(&a, &b) == (0, None) if a > b

fn forward_checked(start: Self, count: usize) -> Option<Self>

Returns the value that would be obtained by taking the successor of self count times.

If this would overflow the range of values supported by Self, returns None.

Invariants

For any a, n, and m:

• Step::forward_checked(a, n).and_then(|x| Step::forward_checked(x, m)) == Step::forward_checked(a, m).and_then(|x| Step::forward_checked(x, n))
• Step::forward_checked(a, n).and_then(|x| Step::forward_checked(x, m)) == try { Step::forward_checked(a, n.checked_add(m)) }

For any a and n:

• Step::forward_checked(a, n) == (0..n).try_fold(a, |x, _| Step::forward_checked(&x, 1))
  • Corollary: Step::forward_checked(a, 0) == Some(a)

fn backward_checked(start: Self, count: usize) -> Option<Self>

Returns the value that would be obtained by taking the predecessor of self count times.

If this would overflow the range of values supported by Self, returns None.

Invariants

For any a, n, and m:

• Step::backward_checked(a, n).and_then(|x| Step::backward_checked(x, m)) == n.checked_add(m).and_then(|x| Step::backward_checked(a, x))
• Step::backward_checked(a, n).and_then(|x| Step::backward_checked(x, m)) == try { Step::backward_checked(a, n.checked_add(m)?) }

For any a and n:

• Step::backward_checked(a, n) == (0..n).try_fold(a, |x, _| Step::backward_checked(x, 1))
  • Corollary: Step::backward_checked(a, 0) == Some(a)

Provided Methods

fn forward(start: Self, count: usize) -> Self

Returns the value that would be obtained by taking the successor of self count times.

If this would overflow the range of values supported by Self, this function is allowed to panic, wrap, or saturate. The suggested behavior is to panic when debug assertions are enabled, and to wrap or saturate otherwise.

Invariants

For any a, n, and m, where no overflow occurs:

• Step::forward(Step::forward(a, n), m) == Step::forward(a, n + m)

For any a and n, where no overflow occurs:

• Step::forward_checked(a, n) == Some(Step::forward(a, n))
• Step::forward(a, n) == (0..n).fold(a, |x, _| Step::forward(x, 1))
  • Corollary: Step::forward(a, 0) == a
• Step::forward(a, n) >= a
• Step::backward(Step::forward(a, n), n) == a

fn backward(start: Self, count: usize) -> Self

Returns the value that would be obtained by taking the predecessor of self count times.

If this would overflow the range of values supported by Self, this function is allowed to panic, wrap, or saturate. The suggested behavior is to panic when debug assertions are enabled, and to wrap or saturate otherwise.

Invariants

For any a, n, and m, where no overflow occurs:

• Step::backward(Step::backward(a, n), m) == Step::backward(a, n + m)

For any a and n, where no overflow occurs:

• Step::backward_checked(a, n) == Some(Step::backward(a, n))
• Step::backward(a, n) == (0..n).fold(a, |x, _| Step::backward(x, 1))
  • Corollary: Step::backward(a, 0) == a
• Step::backward(a, n) <= a
• Step::forward(Step::backward(a, n), n) == a

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementations on Foreign Types

impl Step for i8

fn forward(start: Self, n: usize) -> Self

fn backward(start: Self, n: usize) -> Self

fn steps_between(start: &Self, end: &Self) -> (usize, Option<usize>)

fn forward_checked(start: Self, n: usize) -> Option<Self>

fn backward_checked(start: Self, n: usize) -> Option<Self>

impl Step for i16

fn forward(start: Self, n: usize) -> Self

fn backward(start: Self, n: usize) -> Self

fn steps_between(start: &Self, end: &Self) -> (usize, Option<usize>)

fn forward_checked(start: Self, n: usize) -> Option<Self>

fn backward_checked(start: Self, n: usize) -> Option<Self>

impl Step for i32

fn forward(start: Self, n: usize) -> Self

fn backward(start: Self, n: usize) -> Self

fn steps_between(start: &Self, end: &Self) -> (usize, Option<usize>)

fn forward_checked(start: Self, n: usize) -> Option<Self>

fn backward_checked(start: Self, n: usize) -> Option<Self>

impl Step for i64

fn forward(start: Self, n: usize) -> Self

fn backward(start: Self, n: usize) -> Self

fn steps_between(start: &Self, end: &Self) -> (usize, Option<usize>)

fn forward_checked(start: Self, n: usize) -> Option<Self>

fn backward_checked(start: Self, n: usize) -> Option<Self>

impl Step for i128

fn forward(start: Self, n: usize) -> Self

fn backward(start: Self, n: usize) -> Self

fn steps_between(start: &Self, end: &Self) -> (usize, Option<usize>)

fn forward_checked(start: Self, n: usize) -> Option<Self>

fn backward_checked(start: Self, n: usize) -> Option<Self>

impl Step for isize

fn forward(start: Self, n: usize) -> Self

fn backward(start: Self, n: usize) -> Self

fn steps_between(start: &Self, end: &Self) -> (usize, Option<usize>)

fn forward_checked(start: Self, n: usize) -> Option<Self>

fn backward_checked(start: Self, n: usize) -> Option<Self>

impl Step for u8

fn forward(start: Self, n: usize) -> Self

fn backward(start: Self, n: usize) -> Self

fn steps_between(start: &Self, end: &Self) -> (usize, Option<usize>)

fn forward_checked(start: Self, n: usize) -> Option<Self>

fn backward_checked(start: Self, n: usize) -> Option<Self>

impl Step for u16

fn forward(start: Self, n: usize) -> Self

fn backward(start: Self, n: usize) -> Self

fn steps_between(start: &Self, end: &Self) -> (usize, Option<usize>)

fn forward_checked(start: Self, n: usize) -> Option<Self>

fn backward_checked(start: Self, n: usize) -> Option<Self>

impl Step for u32

fn forward(start: Self, n: usize) -> Self

fn backward(start: Self, n: usize) -> Self

fn steps_between(start: &Self, end: &Self) -> (usize, Option<usize>)

fn forward_checked(start: Self, n: usize) -> Option<Self>

fn backward_checked(start: Self, n: usize) -> Option<Self>

impl Step for u64

fn forward(start: Self, n: usize) -> Self

fn backward(start: Self, n: usize) -> Self

fn steps_between(start: &Self, end: &Self) -> (usize, Option<usize>)

fn forward_checked(start: Self, n: usize) -> Option<Self>

fn backward_checked(start: Self, n: usize) -> Option<Self>

impl Step for u128

fn forward(start: Self, n: usize) -> Self

fn backward(start: Self, n: usize) -> Self

fn steps_between(start: &Self, end: &Self) -> (usize, Option<usize>)

fn forward_checked(start: Self, n: usize) -> Option<Self>

fn backward_checked(start: Self, n: usize) -> Option<Self>

impl Step for usize

fn forward(start: Self, n: usize) -> Self

fn backward(start: Self, n: usize) -> Self

fn steps_between(start: &Self, end: &Self) -> (usize, Option<usize>)

fn forward_checked(start: Self, n: usize) -> Option<Self>

fn backward_checked(start: Self, n: usize) -> Option<Self>

Implementors

impl<T> Step for T

where T: Newtype + Clone + From<T::Inner> + PartialOrd + MinMax, T::Inner: Step,

Blanket Step implementation for all Newtypes.