Struct std::iter::FromFnIterator

A function wrapped in an iterator.

See from_fn for details.

Methods

• fn next(self: &mut FromFnIterator<F, T>) -> Option<T>

  source

  Returns the next item, if any.

  If the iterator has reached the end, it returns Option::none().

  See Iterator for more information.

Mixins

• mixin Iterator<FromFnIterator<F, T>, T>

• fn size_hint(self: &Self) -> Option<usize>

  source

  Returns the number of remaining elements, if available.

  See Iterator for more information.

• mixin IteratorExt<FromFnIterator<F, T>, T>

• fn iter(self: &mut Self) -> &mut Self

  source

  Return self.

  Each iterator is itself an iterable object, though only once. This helper function is there so that iterators can be used ergonomically in for loops (which de-sugar to a call to .iter())

  See also iter.

• fn fuse(self: &mut Self) -> FusedIterator<Self, T>

  source

  Return an iterator that returns Option::none() forever after the first one is returned.

  Iterators can validly reset back to returning values after they are exhausted. This method "caps it off" after they are first exhausted.

• fn chain<Other>(self: &mut Self, other: &mut Other) -> ChainIterator<Self, Other, T>

  Other: Iterator<Other, T>

  source

  Returns an iterator that yields all elements of self and then all elements of other.

  Example

  let range = (0..2).chain(&(10..12));
  assert_eq!(range.size_hint(), Option::some(4usize));
  
  assert_eq!(range.next(), Option::some(0));
  assert_eq!(range.next(), Option::some(1));
  assert_eq!(range.next(), Option::some(10));
  assert_eq!(range.next(), Option::some(11));
  assert_eq!(range.next(), Option::none());
  Run this example

• fn merge_sorted<Other>(self: &mut Self, other: &mut Other) -> MergeIterator<Self, Other, T>

  Other: Iterator<Other, T>

  source

  Returns an iterator that merges two sorted iterators into one sorted iterator.

  T must implement Comparable. If the two iterators are not sorted, the resulting order is unspecified.

  The merge is stable, meaning that the order of equal elements is preserved, with the elements from self coming before the elements from other (and vice-versa if the iterator is reversed/used with next_back).

  Example

  let range = [0, 2, 4].iter().merge_sorted(&[1, 3].iter());
  assert_eq!(range.size_hint(), Option::some(5usize));
  
  assert_eq!(range.next(), Option::some(0));
  assert_eq!(range.next(), Option::some(1));
  assert_eq!(range.next(), Option::some(2));
  assert_eq!(range.next(), Option::some(3));
  assert_eq!(range.next(), Option::some(4));
  assert_eq!(range.next(), Option::none());
  Run this example

• fn skip(self: &mut Self, n: usize) -> SkipIterator<Self, T>

  source

  Returns an iterator that skips first n values.

  If the underlying iterator yields fewer than or exactly n values, then the iterator will yield no values.

  Example

  let range = (0..5).skip(2);
  assert_eq!(range.size_hint(), Option::some(3usize));
  
  assert_eq!(range.next(), Option::some(2));
  assert_eq!(range.next(), Option::some(3));
  assert_eq!(range.next(), Option::some(4));
  assert_eq!(range.next(), Option::none());
  Run this example

• fn step_by(self: &mut Self, n: usize) -> StepByIterator<Self, T>

  source

  Returns an iterator that steps by n values.

  First value will always be yielded, then every n-th value.

  Example

  let range = (0..5).step_by(2);
  assert_eq!(range.size_hint(), Option::some(3usize));
  
  assert_eq!(range.next(), Option::some(0));
  assert_eq!(range.next(), Option::some(2));
  assert_eq!(range.next(), Option::some(4));
  assert_eq!(range.next(), Option::none());
  Run this example

• fn take(self: &mut Self, n: usize) -> TakeIterator<Self, T>

  source

  Returns an iterator that yields at most n elements.

  Example

  let range = (0..5).take(2);
  assert_eq!(range.size_hint(), Option::some(2usize));
  
  assert_eq!(range.next(), Option::some(0));
  assert_eq!(range.next(), Option::some(1));
  assert_eq!(range.next(), Option::none());
  Run this example

• fn enumerate(self: &mut Self) -> EnumerateIterator<Self, T>

  source

  Returns an iterator that attaches a sequence number of each item.

  Example

  let range = (10..15).enumerate();
  assert_eq!(range.size_hint(), Option::some(5usize));
  
  assert_eq!(range.next(), Option::some((0usize, 10)));
  assert_eq!(range.next(), Option::some((1usize, 11)));
  assert_eq!(range.next(), Option::some((2usize, 12)));
  assert_eq!(range.next(), Option::some((3usize, 13)));
  assert_eq!(range.next(), Option::some((4usize, 14)));
  assert_eq!(range.next(), Option::none());
  Run this example

• fn last(self: &mut Self) -> Option<T>

  source

  Returns the last value of the iterator.

  This method always exhausts the iterator. For iterators that implement DoubleEndedIterator, it may be more efficient to use next_back.

  Example

  let last = (0..5).last();
  
  assert_eq!(last, Option::some(4));
  Run this example

• fn nth(self: &mut Self, n: usize) -> Option<T>

  source

  Returns the n-th value of the iterator.

  Example

  let nth = (10..100).nth(2);
  
  assert_eq!(nth, Option::some(12));
  Run this example

• fn count(self: &mut Self) -> usize

  source

  Counts the number of elements in this iterator.

  Example

  let count = (100..105).count();
  
  assert_eq!(count, 5);
  Run this example

• fn inspect<F>(it: &mut Self, func: F) -> InspectIterator<Self, F, T>

  F: Fn(T)

  source

  Inspects each element of the iterator.

  Presented chain of iterator combinators, inspect can be used to execute a callback on every element of an iterator. This is useful for debugging.

  The elements are passed through unmodified.

  Example

  let last = (0..3)
      .iter()
      .inspect(|i: i32| { println!("I see {}", i) })
      .last();
  
  println!("Last: {}", last);
  
  // Prints:
  // I see 0
  // I see 1
  // I see 2
  // Last: 2
  Run this example

• fn take_while<F>(iter: &mut Self, fun: F) -> TakeWhileIterator<Self, F, T>

  F: Fn(T) -> bool

  source

  Returns an iterator that yields the elements while a predicate is true.

  Example

  let range = (0..5).take_while(|x: i32| -> bool { x < 3 });
  assert_eq!(range.size_hint(), Option::none());
  
  assert_eq!(range.next(), Option::some(0));
  assert_eq!(range.next(), Option::some(1));
  assert_eq!(range.next(), Option::some(2));
  assert_eq!(range.next(), Option::none());
  Run this example

• fn skip_while<F>(iter: &mut Self, fun: F) -> SkipWhileIterator<Self, F, T>

  F: Fn(T) -> bool

  source

  Returns an iterator that skips the elements while a predicate is true.

  Example

  let range = (0..5).skip_while(|x: i32| -> bool { x < 3 });
  assert_eq!(range.size_hint(), Option::none());
  
  assert_eq!(range.next(), Option::some(3));
  assert_eq!(range.next(), Option::some(4));
  assert_eq!(range.next(), Option::none());
  Run this example

• fn map<U, F>(iter: &mut Self, fun: F) -> MapIterator<Self, F, T, U>

  F: Fn(T) -> U

  source

  Returns an iterator that transforms the elements of this iterator.

  Example

  let range = (0..5).map(|x: i32| -> i32 { x * 2 });
  assert_eq!(range.size_hint(), Option::some(5usize));
  
  assert_eq!(range.next(), Option::some(0));
  assert_eq!(range.next(), Option::some(2));
  assert_eq!(range.next(), Option::some(4));
  assert_eq!(range.next(), Option::some(6));
  assert_eq!(range.next(), Option::some(8));
  assert_eq!(range.next(), Option::none());
  Run this example

• fn foreach<F>(iter: &mut Self, fun: F)

  F: Fn(T)

  source

  Executes a function on each element of this iterator.

  For readability, it is usually better to use the for loop, but foreach can be useful in cases where a function allocates memory which can be then freed using a defer expression.

  Example

  use std::fmt::format;
  
  (0..5)
      .iter()
      .foreach(|x: i32| {
          let f = format!("{}", x).unwrap();
          defer f.free();
  
          println!("{}", f[..]);
      });
  Run this example

• fn filter<F>(iter: &mut Self, fun: F) -> FilterIterator<Self, F, T>

  F: Fn(T) -> bool

  source

  Returns an iterator that yields the elements of this iterator that match a predicate.

  Example

  let range = (0..5).filter(|x: i32| -> bool { x % 2 == 0 });
  assert_eq!(range.size_hint(), Option::none());
  
  assert_eq!(range.next(), Option::some(0));
  assert_eq!(range.next(), Option::some(2));
  assert_eq!(range.next(), Option::some(4));
  assert_eq!(range.next(), Option::none());
  Run this example

• fn find<F>(iter: &mut Self, fun: F) -> Option<T>

  F: Fn(T) -> bool

  source

  Returns the first item matching the predicate.

  If there is no item matching the predicate, returns none.

  Example

  let a = (1..10).find(|x: i32| -> bool { x * x >= 50 });
  let b = (1..10).find(|x: i32| -> bool { x * x >= 1000 });
  
  assert_eq!(a, Option::some(8));
  assert_eq!(b, Option::none());
  Run this example

• fn find_index<F>(iter: &mut Self, fun: F) -> Option<usize>

  F: Fn(T) -> bool

  source

  Returns the index of the first item matching the predicate.

  If there is no item matching the predicate, returns none.

  Example

  let arr = [1, 2, 3, 1337, 5, 6];
  
  let idx = arr
      .iter()
      .find_index(|x: i32| -> bool { x > 100 })
      .unwrap();
  
  println!("First number larger than 100: {}", arr[idx]);
  Run this example

• fn filter_map<U, F>(iter: &mut Self, fun: F) -> FilterMapIterator<Self, F, T, U>

  F: Fn(T) -> Option<U>

  source

  Transforms and filters the iterator at the same time.

  Function f is called on each element of this iterator. If it returns Option::some(...), that element is yielded. If it returns Option::none(), the element is skipped.

  Example

  let range = (0..6)
      .iter()
      .filter_map(|x: i32| -> Option<i32> {
          if x % 2 == 1 {
              Option::some(x * 100)
          } else {
              Option::none()
          }
      });
  
  assert_eq!(range.next(), Option::some(100));
  assert_eq!(range.next(), Option::some(300));
  assert_eq!(range.next(), Option::some(500));
  Run this example

• fn chunks(self: &mut Self, chunk_size: usize) -> ChunksIterator<Self, T>

  source

  Returns an iterator of chunks of size chunk_size.

  If the iterator is not divisible by chunk_size, the last chunk will be smaller. Panics if chunk_size is 0.

  Example

  // Prints:
  // [ 0 1 2 ]
  // [ 3 4 5 ]
  // [ 6 ]
  for chunk in (0..7).chunks(3) {
      print!("[ ");
      for v in chunk {
          print!("{} ", v);
      }
      println!("]");
  }
  Run this example

• fn reduce<U, F>(iter: &mut Self, initial: U, func: F) -> U

  F: Fn(U, T) -> U

  source

  Reduces the iterator into a single value.

  Equivalent to:

  let value = initial;
  for element in iter {
      value = func(value, element);
  }
  

  Example

  let sum = (0..5)
      .iter()
      .reduce(0, |acc: i32, x: i32| -> i32 { acc + x });
  
  println!("{}", sum); // Prints: 10
  Run this example

• fn sum(iter: &mut Self) -> T

  source

  Sums all the values in the iterator.

  T must satisfy Numeric protocol.

  Example

  let sum = (0..5).sum();
  
  assert_eq!(sum, 10);
  Run this example

• fn min(iter: &mut Self) -> Option<T>

  source

  Returns the minimum value of the iterator.

  T must satisfy Comparable protocol.

  Example

  let min = [1, -5, 10, 200].iter().min();
  
  assert_eq!(min, Option::some(-5));
  Run this example

• fn max(iter: &mut Self) -> Option<T>

  source

  Returns the maximum value of the iterator.

  T must satisfy Comparable protocol.

  Example

  let max = [1, -5, 10, 200].iter().max();
  
  assert_eq!(max, Option::some(200));
  Run this example

• fn all<F>(iter: &mut Self, fun: F) -> bool

  F: Fn(T) -> bool

  source

  Returns true if all elements of the iterator match a predicate, false otherwise.

  If iterator produces no values, true is returned.

  Example

  let t1 = [1, -5, 10, 200].iter().all(|x: i32| -> bool { x > 0 });
  let t2 = [1, -5, 10, 200].iter().all(|x: i32| -> bool { x < 1000 });
  
  assert!(!t1);
  assert!(t2);
  Run this example

• fn any<F>(iter: &mut Self, fun: F) -> bool

  F: Fn(T) -> bool

  source

  Returns true if any element of the iterator matches a predicate, false otherwise.

  If iterator produces no values, false is returned.

  Example

  let t1 = [1, -5, 10, 200].iter().any(|x: i32| -> bool { x > 1000 });
  let t2 = [1, -5, 10, 200].iter().any(|x: i32| -> bool { x < 0 });
  
  assert!(!t1);
  assert!(t2);
  Run this example

• fn to_vector(self: &mut Self) -> Vector<T>

  source

  Collects the values of the iterator into a vector.

  Example

  let range = (0..5).to_vector();
  defer range.free();
  
  assert_eq!(range.len(), 5);
  assert_eq!(range[..], &[0, 1, 2, 3, 4]);
  Run this example

• fn fill_slice(self: &mut Self, slice: &mut [T]) -> usize

  source

  Fills the slice with the values of the iterator.

  If the number of elements in the iterator is greater than the length of the slice, the remaining values in the iterator are not consumed.

  If the number of elements in the iterator is less than the length of the slice, the remainder of the slice is untouched.

  Example

  let buf: [i32; 5];
  (0..5).fill_slice(buf[..]);
  
  assert_eq!(buf[..], &[0, 1, 2, 3, 4]);
  Run this example

• fn peekable(self: &mut Self) -> PeekableIterator<Self, T>

  source

  Returns a "peekable" iterator.

  Peekable iterators have an additional method, peek, which is similar to next, but it does not consume the value, so a subsequent call to next will return the same value.

• fn group_by<F, K>(self: &mut Self, func: F) -> GroupByIterator<Self, F, T, K>

  F: Fn(T) -> K

  K: Equatable<K>

  source

  Returns an iterator of groups grouped by a key.

  Requires that the items of the iterator that have the same key are contiguous (e.g. the values are sorted by key).

  Example

  fn divide_by_three(x: i32) -> i32 { x / 3 }
  
  for group in (0..10).group_by(divide_by_three) {
      print!("{}:", group.key);
      for value in group {
          print!(" {}", value);
      }
      println!("");
  }
  
  // Prints:
  // 0: 0 1 2
  // 1: 3 4 5
  // 2: 6 7 8
  // 3: 9
  Run this example

• fn zip<Other>(self: &mut Self, other: &mut Other) -> ZipIterator<Self, Other, T, iterator_yield_t<Other>>

  source

  Combines two iterators, returning an iterator of pairs.

  Example

  let iter = (0..5).zip(&(10..15));
  
  assert_eq!(iter.size_hint(), Option::some(5usize));
  
  assert_eq!(iter.next(), Option::some((0, 10)));
  assert_eq!(iter.next(), Option::some((1, 11)));
  assert_eq!(iter.next(), Option::some((2, 12)));
  assert_eq!(iter.next(), Option::some((3, 13)));
  assert_eq!(iter.next(), Option::some((4, 14)));
  assert_eq!(iter.next(), Option::none());
  Run this example

• fn flatten(self: &mut Self) -> FlattenIterator<Self, T, iterable_yield_t<T>>

  source

  Flattens an iterator over iterable types into a single iterator.

  Example

  let iter = ["Hello", " ", "World"].iter().flatten();
  
  let v = iter.to_vector();
  defer v.free();
  
  assert_eq!(v[..], &['H', 'e', 'l', 'l', 'o', ' ', 'W', 'o', 'r', 'l', 'd']);
  Run this example