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

     1  package linkedliststack
     2  
     3  import "github.com/songzhibin97/go-baseutils/structure/containers"
     4  
     5  // Assert Iterator implementation
     6  var _ containers.IteratorWithIndex[any] = (*Iterator[any])(nil)
     7  
     8  // Iterator returns a stateful iterator whose values can be fetched by an index.
     9  type Iterator[E any] struct {
    10  	stack *Stack[E]
    11  	index int
    12  }
    13  
    14  // Iterator returns a stateful iterator whose values can be fetched by an index.
    15  func (stack *Stack[E]) Iterator() Iterator[E] {
    16  	return Iterator[E]{stack: stack, 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.stack.Size() {
    25  		iterator.index++
    26  	}
    27  	return iterator.stack.withinRange(iterator.index)
    28  }
    29  
    30  // Value returns the current element's value.
    31  // Does not modify the state of the iterator.
    32  func (iterator *Iterator[E]) Value() E {
    33  	value, _ := iterator.stack.list.Get(iterator.index) // in reverse (LIFO)
    34  	return value
    35  }
    36  
    37  // Index returns the current element's index.
    38  // Does not modify the state of the iterator.
    39  func (iterator *Iterator[E]) Index() int {
    40  	return iterator.index
    41  }
    42  
    43  // Begin resets the iterator to its initial state (one-before-first)
    44  // Call Next() to fetch the first element if any.
    45  func (iterator *Iterator[E]) Begin() {
    46  	iterator.index = -1
    47  }
    48  
    49  // First moves the iterator to the first element and returns true if there was a first element in the container.
    50  // If First() returns true, then first element's index and value can be retrieved by Index() and Value().
    51  // Modifies the state of the iterator.
    52  func (iterator *Iterator[E]) First() bool {
    53  	iterator.Begin()
    54  	return iterator.Next()
    55  }
    56  
    57  // NextTo moves the iterator to the next element from current position that satisfies the condition given by the
    58  // passed function, and returns true if there was a next element in the container.
    59  // If NextTo() returns true, then next element's index and value can be retrieved by Index() and Value().
    60  // Modifies the state of the iterator.
    61  func (iterator *Iterator[E]) NextTo(f func(index int, value E) bool) bool {
    62  	for iterator.Next() {
    63  		index, value := iterator.Index(), iterator.Value()
    64  		if f(index, value) {
    65  			return true
    66  		}
    67  	}
    68  	return false
    69  }