Struct Punctuated 

pub struct Punctuated<T, P>(/* private fields */);

A punctuated sequence with optional trailing separator.

Use this for lists where trailing punctuation is allowed but not required, such as array literals: [1, 2, 3] or [1, 2, 3,].

Type Parameters

• T: The value type (e.g., expression)
• P: The punctuation/separator type (e.g., comma token)

Example

// Parse: item, item, item
let mut items = Punctuated::<Item, CommaToken>::new();
items.push_value(stream.parse()?);
while stream.peek::<CommaToken>() {
    items.push_punct(stream.parse()?);
    if !stream.peek::<Item>() { break; } // Allow trailing comma
    items.push_value(stream.parse()?);
}

Implementations

impl<T, P> Punctuated<T, P>

pub const POLICY: TrailingPolicy = TrailingPolicy::Optional

The trailing punctuation policy for this type.

pub fn new() -> Self

Creates a new empty sequence.

pub fn with_capacity(capacity: usize) -> Self

Creates a new sequence with pre-allocated capacity.

pub fn push_value(&mut self, value: T)

Pushes a value onto the sequence.

pub fn push_punct(&mut self, punct: P)

Attaches punctuation to the last value.

pub fn trailing_punct(&self) -> bool

Returns whether the sequence has trailing punctuation.

The return value depends on the wrapper type’s policy:

• Punctuated: delegates to inner storage
• Terminated: always true
• Separated: always false

pub fn into_inner(self) -> PunctuatedInner<T, P>

Consumes the wrapper and returns the inner storage.

Methods from Deref<Target = PunctuatedInner<T, P>>

pub fn push_value(&mut self, value: T)

pub fn push_punct(&mut self, punct: P)

pub fn trailing_punct(&self) -> bool

pub fn len(&self) -> usize

pub fn is_empty(&self) -> bool

pub fn capacity(&self) -> usize

pub fn reserve(&mut self, additional: usize)

pub fn shrink_to_fit(&mut self)

pub fn clear(&mut self)

pub fn iter(&self) -> impl Iterator<Item = &T>

pub fn iter_mut(&mut self) -> impl Iterator<Item = &mut T>

pub fn pairs(&self) -> impl Iterator<Item = (&T, Option<&P>)>

pub fn pairs_mut(&mut self) -> impl Iterator<Item = (&mut T, Option<&mut P>)>

pub fn first(&self) -> Option<&T>

pub fn last(&self) -> Option<&T>

Trait Implementations

impl<T, P> AsMut<PunctuatedInner<T, P>> for Punctuated<T, P>

fn as_mut(&mut self) -> &mut PunctuatedInner<T, P>

Converts this type into a mutable reference of the (usually inferred) input type.

impl<T, P> AsRef<PunctuatedInner<T, P>> for Punctuated<T, P>

fn as_ref(&self) -> &PunctuatedInner<T, P>

Converts this type into a shared reference of the (usually inferred) input type.

impl<T: Clone, P: Clone> Clone for Punctuated<T, P>

fn clone(&self) -> Punctuated<T, P>

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T: Debug, P: Debug> Debug for Punctuated<T, P>

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

Formats the value using the given formatter.

impl<T, P> Default for Punctuated<T, P>

fn default() -> Self

Returns the “default value” for a type.

impl<T, P> Deref for Punctuated<T, P>

type Target = PunctuatedInner<T, P>

The resulting type after dereferencing.

fn deref(&self) -> &Self::Target

Dereferences the value.

impl<T, P> DerefMut for Punctuated<T, P>

fn deref_mut(&mut self) -> &mut Self::Target

Mutably dereferences the value.

impl<T, P> FromIterator<T> for Punctuated<T, P>

fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Self

Creates a value from an iterator.

impl<T, P> IntoIterator for Punctuated<T, P>

type Item = T

The type of the elements being iterated over.

type IntoIter = Map<IntoIter<(T, Option<P>)>, fn((T, Option<P>)) -> T>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.