Swift higher-order functions contain allSatisfy reversed lexicographicallyPrecedes usage example

1. contains

Returns a Boolean value indicating whether each element of the sequence satisfies the given condition. If one is satisfied, it will return.

     let expenses = [21.37, 55.21, 9.32, 10.18, 388.77, 11.41]
     let hasBigPurchase =  { $0 > 100 }
     // 'hasBigPurchase' == true

SequenceProtocol source code

  @inlinable
  public func contains(_ element: Element) -> Bool {
    if let result = _customContainsEquatableElement(element) {
      return result
    } else {
      return  { $0 == element }
    }
  }

  @inlinable
  public func contains(
    where predicate: (Element) throws -> Bool
  ) rethrows -> Bool {
    for e in self {
      if try predicate(e) {
        return true
      }
    }
    return false
  }

2. allSatisfy

Returns a Boolean value indicating whether each element of the sequence satisfies the given condition. All elements need to be satisfied.

        let names = ["Sofia", "Camilla", "Martina", "Mateo", "Nicolás"]
        let allHaveAtLeastFive = ({ $ >= 5 })
        // allHaveAtLeastFive == true

SequenceProtocol source code

allSatisfyCalled insidecontainsmethod

  @inlinable
  public func allSatisfy(
    _ predicate: (Element) throws -> Bool
  ) rethrows -> Bool {
    return try !contains { try !predicate($0) }
  }

3. reversed

Returns an array containing the elements of this sequence in reverse order.

let list = [1, 2, 3, 4, 5]
let ret = ()
print(Array(ret))
---console
[5, 4, 3, 2, 1]

SequenceProtocol source code

  @inlinable
  public __consuming func reversed() -> [Element] {
    // FIXME(performance): optimize to 1 pass?  But Array(self) can be
    // optimized to a memcpy() sometimes.  Those cases are usually collections,
    // though.
    var result = Array(self)
    let count = 
    for i in 0..<count/2 {
      (i, count - ((i + 1) as Int))
    }
    return result
  }

4. Lexicographically Precedes

Returns a Boolean value indicating whether the sequence is before another sequence in dictionary order (dictionary) and the elements are compared using the given conditional statement.

let list = [1, 2, 3, 4, 5]
let list2 = [2, 2, 3, 5]
let ret1 = (list2)
let ret2 = (list)
print(ret1, ret2)
---console
true false

SequenceProtocol source code

  @inlinable
  public func lexicographicallyPrecedes<OtherSequence: Sequence>(
    _ other: OtherSequence
  ) -> Bool where  == Element {
    return (other, by: <)
  }

  @inlinable
  public func lexicographicallyPrecedes<OtherSequence: Sequence>(
    _ other: OtherSequence,
    by areInIncreasingOrder: (Element, Element) throws -> Bool
  ) rethrows -> Bool 
  where  == Element {
    var iter1 = ()
    var iter2 = ()
    while true {
      if let e1 = () {
        if let e2 = () {
          if try areInIncreasingOrder(e1, e2) {
            return true
          }
          if try areInIncreasingOrder(e2, e1) {
            return false
          }
          continue // Equivalent
        }
        return false
      }
      return () != nil
    }
  }

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