# Struct std::ops::RangeTo

1.0.0 · source ·

    pub struct RangeTo<Idx> {
        pub end: Idx,
    }

Expand description

A range only bounded exclusively above (`..end`).

The `RangeTo` `..end` contains all values with `x < end`. It cannot serve as an `Iterator` because it doesn’t have a starting point.

## Examples

The `..end` syntax is a `RangeTo`:

    assert_eq!((..5), std::ops::RangeTo { end: 5 });

Run

It does not have an `IntoIterator` implementation, so you can’t use it in a `for` loop directly. This won’t compile:

ⓘ

    // error[E0277]: the trait bound `std::ops::RangeTo<{integer}>:
    // std::iter::Iterator` is not satisfied
    for i in ..5 {
        // ...
    }

Run

When used as a slicing index, `RangeTo` produces a slice of all array elements before the index indicated by `end`.

    let arr = [0, 1, 2, 3, 4];
    assert_eq!(arr[ ..  ], [0, 1, 2, 3, 4]);
    assert_eq!(arr[ .. 3], [0, 1, 2      ]); // This is a `RangeTo`
    assert_eq!(arr[ ..=3], [0, 1, 2, 3   ]);
    assert_eq!(arr[1..  ], [   1, 2, 3, 4]);
    assert_eq!(arr[1.. 3], [   1, 2      ]);
    assert_eq!(arr[1..=3], [   1, 2, 3   ]);

Run

## Fields§

§`end: Idx`

The upper bound of the range (exclusive).

## Implementations§

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### impl<Idx> RangeTo<Idx>where Idx: PartialOrd,

1.35.0 · source

#### pub fn contains<U>(&self, item: &U) -> bool where Idx: PartialOrd<U>, U: PartialOrd<Idx> + ?Sized,

Returns `true` if `item` is contained in the range.

##### Examples

    assert!( (..5).contains(&-1_000_000_000));
    assert!( (..5).contains(&4));
    assert!(!(..5).contains(&5));

    assert!( (..1.0).contains(&0.5));
    assert!(!(..1.0).contains(&f32::NAN));
    assert!(!(..f32::NAN).contains(&0.5));

Run

## Trait Implementations§

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### impl<Idx> Clone for RangeTo<Idx>where Idx: Clone,

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#### fn clone(&self) -> RangeTo<Idx>

Returns a copy of the value. Read more
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#### fn clone_from(&mut self, source: &Self)

Performs copy-assignment from `source`. Read more
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### impl<Idx> Debug for RangeTo<Idx>where Idx: Debug,

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#### fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter. Read more
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### impl<Idx> Hash for RangeTo<Idx>where Idx: Hash,

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#### fn hash<__H>(&self, state: &mut __H)where __H: Hasher,

Feeds this value into the given `Hasher`. Read more
1.3.0 · source§

#### fn hash_slice<H>(data: &[Self], state: &mut H)where H: Hasher, Self: Sized,

Feeds a slice of this type into the given `Hasher`. Read more
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### impl Index<RangeTo<usize>> for String

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#### type Output = str

The returned type after indexing.
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#### fn index(&self, index: RangeTo<usize>) -> &str

Performs the indexing (`container[index]`) operation. Read more
1.3.0 · source§

### impl IndexMut<RangeTo<usize>> for String

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#### fn index_mut(&mut self, index: RangeTo<usize>) -> &mut str

Performs the mutable indexing (`container[index]`) operation. Read more
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### impl<Idx> PartialEq for RangeTo<Idx>where Idx: PartialEq,

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#### fn eq(&self, other: &RangeTo<Idx>) -> bool

This method tests for `self` and `other` values to be equal, and is used by `==`.
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#### fn ne(&self, other: &Rhs) -> bool

This method tests for `!=`. The default implementation is almost always sufficient, and should not be overridden without very good reason.
1.28.0 · source§

### impl<T> RangeBounds<T> for RangeTo<&T>

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#### fn start_bound(&self) -> Bound<&T>

Start index bound. Read more
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#### fn end_bound(&self) -> Bound<&T>

End index bound. Read more
1.35.0 · source§

#### fn contains<U>(&self, item: &U) -> bool where T: PartialOrd<U>, U: PartialOrd<T> + ?Sized,

Returns `true` if `item` is contained in the range. Read more
1.28.0 · source§

### impl<T> RangeBounds<T> for RangeTo<T>

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#### fn start_bound(&self) -> Bound<&T>

Start index bound. Read more
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#### fn end_bound(&self) -> Bound<&T>

End index bound. Read more
1.35.0 · source§

#### fn contains<U>(&self, item: &U) -> bool where T: PartialOrd<U>, U: PartialOrd<T> + ?Sized,

Returns `true` if `item` is contained in the range. Read more
1.15.0 (const: unstable) · source§

### impl<T> SliceIndex<[T]> for RangeTo<usize>

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#### type Output = [T]

The output type returned by methods.
const: unstable · source§

#### fn get(self, slice: &[T]) -> Option<&[T]>

🔬This is a nightly-only experimental API. (`slice_index_methods`)
Returns a shared reference to the output at this location, if in bounds.
const: unstable · source§

#### fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]>

🔬This is a nightly-only experimental API. (`slice_index_methods`)
Returns a mutable reference to the output at this location, if in bounds.
const: unstable · source§

#### unsafe fn get_unchecked(self, slice: *const [T]) -> *const [T]

🔬This is a nightly-only experimental API. (`slice_index_methods`)
Returns a shared reference to the output at this location, without performing any bounds checking. Calling this method with an out-of-bounds index or a dangling `slice` pointer is undefined behavior even if the resulting reference is not used.
const: unstable · source§

#### unsafe fn get_unchecked_mut(self, slice: *mut [T]) -> *mut [T]

🔬This is a nightly-only experimental API. (`slice_index_methods`)
Returns a mutable reference to the output at this location, without performing any bounds checking. Calling this method with an out-of-bounds index or a dangling `slice` pointer is undefined behavior even if the resulting reference is not used.
const: unstable · source§

#### fn index(self, slice: &[T]) -> &[T]

🔬This is a nightly-only experimental API. (`slice_index_methods`)
Returns a shared reference to the output at this location, panicking if out of bounds.
const: unstable · source§

#### fn index_mut(self, slice: &mut [T]) -> &mut [T]

🔬This is a nightly-only experimental API. (`slice_index_methods`)
Returns a mutable reference to the output at this location, panicking if out of bounds.
1.20.0 (const: unstable) · source§

### impl SliceIndex<str> for RangeTo<usize>

Implements substring slicing with syntax `&self[.. end]` or `&mut self[.. end]`.

Returns a slice of the given string from the byte range [0, `end`). Equivalent to `&self[0 .. end]` or `&mut self[0 .. end]`.

This operation is O(1).

Prior to 1.20.0, these indexing operations were still supported by direct implementation of `Index` and `IndexMut`.

#### Panics

Panics if `end` does not point to the starting byte offset of a character (as defined by `is_char_boundary`), or if `end > len`.

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#### type Output = str

The output type returned by methods.
const: unstable · source§

#### fn get( self, slice: &str ) -> Option<&<RangeTo<usize> as SliceIndex<str>>::Output>

🔬This is a nightly-only experimental API. (`slice_index_methods`)
Returns a shared reference to the output at this location, if in bounds.
const: unstable · source§

#### fn get_mut( self, slice: &mut str ) -> Option<&mut <RangeTo<usize> as SliceIndex<str>>::Output>

🔬This is a nightly-only experimental API. (`slice_index_methods`)
Returns a mutable reference to the output at this location, if in bounds.
const: unstable · source§

#### unsafe fn get_unchecked( self, slice: *const str ) -> *const <RangeTo<usize> as SliceIndex<str>>::Output

🔬This is a nightly-only experimental API. (`slice_index_methods`)
Returns a shared reference to the output at this location, without performing any bounds checking. Calling this method with an out-of-bounds index or a dangling `slice` pointer is undefined behavior even if the resulting reference is not used.
const: unstable · source§

#### unsafe fn get_unchecked_mut( self, slice: *mut str ) -> *mut <RangeTo<usize> as SliceIndex<str>>::Output

🔬This is a nightly-only experimental API. (`slice_index_methods`)
Returns a mutable reference to the output at this location, without performing any bounds checking. Calling this method with an out-of-bounds index or a dangling `slice` pointer is undefined behavior even if the resulting reference is not used.
const: unstable · source§

#### fn index(self, slice: &str) -> &<RangeTo<usize> as SliceIndex<str>>::Output

🔬This is a nightly-only experimental API. (`slice_index_methods`)
Returns a shared reference to the output at this location, panicking if out of bounds.
const: unstable · source§

#### fn index_mut( self, slice: &mut str ) -> &mut <RangeTo<usize> as SliceIndex<str>>::Output

🔬This is a nightly-only experimental API. (`slice_index_methods`)
Returns a mutable reference to the output at this location, panicking if out of bounds.
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### impl<Idx> Copy for RangeTo<Idx>where Idx: Copy,

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### impl<Idx> Eq for RangeTo<Idx>where Idx: Eq,

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### impl<T> OneSidedRange<T> for RangeTo<T>where RangeTo<T>: RangeBounds<T>,

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### impl<Idx> StructuralEq for RangeTo<Idx>

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### impl<Idx> StructuralPartialEq for RangeTo<Idx>

## Auto Trait Implementations§

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### impl<Idx> RefUnwindSafe for RangeTo<Idx>where Idx: RefUnwindSafe,

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### impl<Idx> Send for RangeTo<Idx>where Idx: Send,

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### impl<Idx> Sync for RangeTo<Idx>where Idx: Sync,

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### impl<Idx> Unpin for RangeTo<Idx>where Idx: Unpin,

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### impl<Idx> UnwindSafe for RangeTo<Idx>where Idx: UnwindSafe,

## Blanket Implementations§

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### impl<T> Any for Twhere T: 'static + ?Sized,

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#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more
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### impl<T> Borrow<T> for Twhere T: ?Sized,

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#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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### impl<T> BorrowMut<T> for Twhere T: ?Sized,

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#### fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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### impl<T> From<T> for T

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#### fn from(t: T) -> T

Returns the argument unchanged.

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### impl<T, U> Into<U> for Twhere U: From<T>,

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#### fn into(self) -> U

Calls `U::from(self)`.

That is, this conversion is whatever the implementation of `From<T> for U` chooses to do.

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### impl<T> ToOwned for Twhere T: Clone,

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#### type Owned = T

The resulting type after obtaining ownership.
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#### fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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#### fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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### impl<T, U> TryFrom<U> for Twhere U: Into<T>,

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#### type Error = Infallible

The type returned in the event of a conversion error.
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#### fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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### impl<T, U> TryInto<U> for Twhere U: TryFrom<T>,

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#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.