maps.go

Documentation: maps

     1  // Copyright 2021 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // Package maps defines various functions useful with maps of any type.
     6  package maps
     7  
     8  // Equal reports whether two maps contain the same key/value pairs.
     9  // Values are compared using ==.
    10  func Equal[M1, M2 ~map[K]V, K, V comparable](m1 M1, m2 M2) bool {
    11  	if len(m1) != len(m2) {
    12  		return false
    13  	}
    14  	for k, v1 := range m1 {
    15  		if v2, ok := m2[k]; !ok || v1 != v2 {
    16  			return false
    17  		}
    18  	}
    19  	return true
    20  }
    21  
    22  // EqualFunc is like Equal, but compares values using eq.
    23  // Keys are still compared with ==.
    24  func EqualFunc[M1 ~map[K]V1, M2 ~map[K]V2, K comparable, V1, V2 any](m1 M1, m2 M2, eq func(V1, V2) bool) bool {
    25  	if len(m1) != len(m2) {
    26  		return false
    27  	}
    28  	for k, v1 := range m1 {
    29  		if v2, ok := m2[k]; !ok || !eq(v1, v2) {
    30  			return false
    31  		}
    32  	}
    33  	return true
    34  }
    35  
    36  // clone is implemented in the runtime package.
    37  func clone(m any) any
    38  
    39  // Clone returns a copy of m.  This is a shallow clone:
    40  // the new keys and values are set using ordinary assignment.
    41  func Clone[M ~map[K]V, K comparable, V any](m M) M {
    42  	// Preserve nil in case it matters.
    43  	if m == nil {
    44  		return nil
    45  	}
    46  	return clone(m).(M)
    47  }
    48  
    49  // Copy copies all key/value pairs in src adding them to dst.
    50  // When a key in src is already present in dst,
    51  // the value in dst will be overwritten by the value associated
    52  // with the key in src.
    53  func Copy[M1 ~map[K]V, M2 ~map[K]V, K comparable, V any](dst M1, src M2) {
    54  	for k, v := range src {
    55  		dst[k] = v
    56  	}
    57  }
    58  
    59  // DeleteFunc deletes any key/value pairs from m for which del returns true.
    60  func DeleteFunc[M ~map[K]V, K comparable, V any](m M, del func(K, V) bool) {
    61  	for k, v := range m {
    62  		if del(k, v) {
    63  			delete(m, k)
    64  		}
    65  	}
    66  }
    67
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