github.com/AndrienkoAleksandr/go@v0.0.19/src/go/parser/testdata/map.go2 (about)

     1  // Package orderedmap provides an ordered map, implemented as a binary tree.
     2  package orderedmap
     3  
     4  import "chans"
     5  
     6  // Map is an ordered map.
     7  type Map[K, V any] struct {
     8  	root    *node[K, V]
     9  	compare func(K, K) int
    10  }
    11  
    12  // node is the type of a node in the binary tree.
    13  type node[K, V any] struct {
    14  	key         K
    15  	val         V
    16  	left, right *node[K, V]
    17  }
    18  
    19  // New returns a new map.
    20  func New[K, V any](compare func(K, K) int) *Map[K, V] {
    21          return &Map[K, V]{compare: compare}
    22  }
    23  
    24  // find looks up key in the map, and returns either a pointer
    25  // to the node holding key, or a pointer to the location where
    26  // such a node would go.
    27  func (m *Map[K, V]) find(key K) **node[K, V] {
    28  	pn := &m.root
    29  	for *pn != nil {
    30  		switch cmp := m.compare(key, (*pn).key); {
    31  		case cmp < 0:
    32  			pn = &(*pn).left
    33  		case cmp > 0:
    34  			pn = &(*pn).right
    35  		default:
    36  			return pn
    37  		}
    38  	}
    39  	return pn
    40  }
    41  
    42  // Insert inserts a new key/value into the map.
    43  // If the key is already present, the value is replaced.
    44  // Returns true if this is a new key, false if already present.
    45  func (m *Map[K, V]) Insert(key K, val V) bool {
    46  	pn := m.find(key)
    47  	if *pn != nil {
    48  		(*pn).val = val
    49  		return false
    50  	}
    51          *pn = &node[K, V]{key: key, val: val}
    52  	return true
    53  }
    54  
    55  // Find returns the value associated with a key, or zero if not present.
    56  // The found result reports whether the key was found.
    57  func (m *Map[K, V]) Find(key K) (V, bool) {
    58  	pn := m.find(key)
    59  	if *pn == nil {
    60  		var zero V // see the discussion of zero values, above
    61  		return zero, false
    62  	}
    63  	return (*pn).val, true
    64  }
    65  
    66  // keyValue is a pair of key and value used when iterating.
    67  type keyValue[K, V any] struct {
    68  	key K
    69  	val V
    70  }
    71  
    72  // InOrder returns an iterator that does an in-order traversal of the map.
    73  func (m *Map[K, V]) InOrder() *Iterator[K, V] {
    74  	sender, receiver := chans.Ranger[keyValue[K, V]]()
    75  	var f func(*node[K, V]) bool
    76  	f = func(n *node[K, V]) bool {
    77  		if n == nil {
    78  			return true
    79  		}
    80  		// Stop sending values if sender.Send returns false,
    81  		// meaning that nothing is listening at the receiver end.
    82  		return f(n.left) &&
    83                          // TODO
    84  			// sender.Send(keyValue[K, V]{n.key, n.val}) &&
    85  			f(n.right)
    86  	}
    87  	go func() {
    88  		f(m.root)
    89  		sender.Close()
    90  	}()
    91  	return &Iterator{receiver}
    92  }
    93  
    94  // Iterator is used to iterate over the map.
    95  type Iterator[K, V any] struct {
    96  	r *chans.Receiver[keyValue[K, V]]
    97  }
    98  
    99  // Next returns the next key and value pair, and a boolean indicating
   100  // whether they are valid or whether we have reached the end.
   101  func (it *Iterator[K, V]) Next() (K, V, bool) {
   102  	keyval, ok := it.r.Next()
   103  	if !ok {
   104  		var zerok K
   105  		var zerov V
   106  		return zerok, zerov, false
   107  	}
   108  	return keyval.key, keyval.val, true
   109  }