github.com/songzhibin97/go-baseutils@v0.0.2-0.20240302024150-487d8ce9c082/structure/lists/arraylist/iterator.go (about)

     1  package arraylist
     2  
     3  import "github.com/songzhibin97/go-baseutils/structure/containers"
     4  
     5  // Assert Iterator implementation
     6  var _ containers.ReverseIteratorWithIndex[any] = (*Iterator[any])(nil)
     7  
     8  // Iterator holding the iterator's state
     9  type Iterator[E any] struct {
    10  	list  *List[E]
    11  	index int
    12  }
    13  
    14  // Iterator returns a stateful iterator whose values can be fetched by an index.
    15  func (l *List[E]) Iterator() Iterator[E] {
    16  	return Iterator[E]{list: l, index: -1}
    17  }
    18  
    19  // Next moves the iterator to the next element and returns true if there was a next element in the container.
    20  // If Next() returns true, then next element's index and value can be retrieved by Index() and Value().
    21  // If Next() was called for the first time, then it will point the iterator to the first element if it exists.
    22  // Modifies the state of the iterator.
    23  func (iterator *Iterator[E]) Next() bool {
    24  	if iterator.index < iterator.list.size {
    25  		iterator.index++
    26  	}
    27  	return iterator.list.withinRange(iterator.index)
    28  }
    29  
    30  // Prev moves the iterator to the previous element and returns true if there was a previous element in the container.
    31  // If Prev() returns true, then previous element's index and value can be retrieved by Index() and Value().
    32  // Modifies the state of the iterator.
    33  func (iterator *Iterator[E]) Prev() bool {
    34  	if iterator.index >= 0 {
    35  		iterator.index--
    36  	}
    37  	return iterator.list.withinRange(iterator.index)
    38  }
    39  
    40  // Value returns the current element's value.
    41  // Does not modify the state of the iterator.
    42  func (iterator *Iterator[E]) Value() E {
    43  	return iterator.list.elements[iterator.index]
    44  }
    45  
    46  // Index returns the current element's index.
    47  // Does not modify the state of the iterator.
    48  func (iterator *Iterator[E]) Index() int {
    49  	return iterator.index
    50  }
    51  
    52  // Begin resets the iterator to its initial state (one-before-first)
    53  // Call Next() to fetch the first element if any.
    54  func (iterator *Iterator[E]) Begin() {
    55  	iterator.index = -1
    56  }
    57  
    58  // End moves the iterator past the last element (one-past-the-end).
    59  // Call Prev() to fetch the last element if any.
    60  func (iterator *Iterator[E]) End() {
    61  	iterator.index = iterator.list.size
    62  }
    63  
    64  // First moves the iterator to the first element and returns true if there was a first element in the container.
    65  // If First() returns true, then first element's index and value can be retrieved by Index() and Value().
    66  // Modifies the state of the iterator.
    67  func (iterator *Iterator[E]) First() bool {
    68  	iterator.Begin()
    69  	return iterator.Next()
    70  }
    71  
    72  // Last moves the iterator to the last element and returns true if there was a last element in the container.
    73  // If Last() returns true, then last element's index and value can be retrieved by Index() and Value().
    74  // Modifies the state of the iterator.
    75  func (iterator *Iterator[E]) Last() bool {
    76  	iterator.End()
    77  	return iterator.Prev()
    78  }
    79  
    80  // NextTo moves the iterator to the next element from current position that satisfies the condition given by the
    81  // passed function, and returns true if there was a next element in the container.
    82  // If NextTo() returns true, then next element's index and value can be retrieved by Index() and Value().
    83  // Modifies the state of the iterator.
    84  func (iterator *Iterator[E]) NextTo(f func(index int, value E) bool) bool {
    85  	for iterator.Next() {
    86  		index, value := iterator.Index(), iterator.Value()
    87  		if f(index, value) {
    88  			return true
    89  		}
    90  	}
    91  	return false
    92  }
    93  
    94  // PrevTo moves the iterator to the previous element from current position that satisfies the condition given by the
    95  // passed function, and returns true if there was a next element in the container.
    96  // If PrevTo() returns true, then next element's index and value can be retrieved by Index() and Value().
    97  // Modifies the state of the iterator.
    98  func (iterator *Iterator[E]) PrevTo(f func(index int, value E) bool) bool {
    99  	for iterator.Prev() {
   100  		index, value := iterator.Index(), iterator.Value()
   101  		if f(index, value) {
   102  			return true
   103  		}
   104  	}
   105  	return false
   106  }