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  //
     7  // This package does not have any special handling for non-reflexive keys
     8  // (keys k where k != k), such as floating-point NaNs.
     9  package maps
    10  
    11  import (
    12  	_ "unsafe"
    13  )
    14  
    15  // Equal reports whether two maps contain the same key/value pairs.
    16  // Values are compared using ==.
    17  func Equal[M1, M2 ~map[K]V, K, V comparable](m1 M1, m2 M2) bool {
    18  	if len(m1) != len(m2) {
    19  		return false
    20  	}
    21  	for k, v1 := range m1 {
    22  		if v2, ok := m2[k]; !ok || v1 != v2 {
    23  			return false
    24  		}
    25  	}
    26  	return true
    27  }
    28  
    29  // EqualFunc is like Equal, but compares values using eq.
    30  // Keys are still compared with ==.
    31  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 {
    32  	if len(m1) != len(m2) {
    33  		return false
    34  	}
    35  	for k, v1 := range m1 {
    36  		if v2, ok := m2[k]; !ok || !eq(v1, v2) {
    37  			return false
    38  		}
    39  	}
    40  	return true
    41  }
    42  
    43  // clone is implemented in the runtime package.
    44  //
    45  //go:linkname clone maps.clone
    46  func clone(m any) any
    47  
    48  // Clone returns a copy of m.  This is a shallow clone:
    49  // the new keys and values are set using ordinary assignment.
    50  func Clone[M ~map[K]V, K comparable, V any](m M) M {
    51  	// Preserve nil in case it matters.
    52  	if m == nil {
    53  		return nil
    54  	}
    55  	return clone(m).(M)
    56  }
    57  
    58  // Copy copies all key/value pairs in src adding them to dst.
    59  // When a key in src is already present in dst,
    60  // the value in dst will be overwritten by the value associated
    61  // with the key in src.
    62  func Copy[M1 ~map[K]V, M2 ~map[K]V, K comparable, V any](dst M1, src M2) {
    63  	for k, v := range src {
    64  		dst[k] = v
    65  	}
    66  }
    67  
    68  // DeleteFunc deletes any key/value pairs from m for which del returns true.
    69  func DeleteFunc[M ~map[K]V, K comparable, V any](m M, del func(K, V) bool) {
    70  	for k, v := range m {
    71  		if del(k, v) {
    72  			delete(m, k)
    73  		}
    74  	}
    75  }
    76
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