Package maps

import "maps"

Overview ▸

Overview ▾

Package maps defines various functions useful with maps of any type.

This package does not have any special handling for non-reflexive keys (keys k where k != k), such as floating-point NaNs.

Index ▸

Index ▾

func All[Map ~map[K]V, K comparable, V any](m Map) iter.Seq2[K, V]

func Clone[M ~map[K]V, K comparable, V any](m M) M

func Collect[K comparable, V any](seq iter.Seq2[K, V]) map[K]V

func Copy[M1 ~map[K]V, M2 ~map[K]V, K comparable, V any](dst M1, src M2)

func DeleteFunc[M ~map[K]V, K comparable, V any](m M, del func(K, V) bool)

func Equal[M1, M2 ~map[K]V, K, V comparable](m1 M1, m2 M2) bool

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

func Insert[Map ~map[K]V, K comparable, V any](m Map, seq iter.Seq2[K, V])

func Keys[Map ~map[K]V, K comparable, V any](m Map) iter.Seq[K]

func Values[Map ~map[K]V, K comparable, V any](m Map) iter.Seq[V]

Examples (Expand All)

Package files

iter.go maps.go

func All ¶

func All[Map ~map[K]V, K comparable, V any](m Map) iter.Seq2[K, V]

All returns an iterator over key-value pairs from m. The iteration order is not specified and is not guaranteed to be the same from one call to the next.

▸ Example

▾ Example

package main

import (
	"fmt"
	"maps"
)

func main() {
	m1 := map[string]int{
		"one": 1,
		"two": 2,
	}
	m2 := map[string]int{
		"one": 10,
	}
	maps.Insert(m2, maps.All(m1))
	fmt.Println("m2 is:", m2)
}

m2 is: map[one:1 two:2]

func Clone ¶

func Clone[M ~map[K]V, K comparable, V any](m M) M

Clone returns a copy of m. This is a shallow clone: the new keys and values are set using ordinary assignment.

▸ Example

▾ Example

package main

import (
	"fmt"
	"maps"
)

func main() {
	m1 := map[string]int{
		"key": 1,
	}
	m2 := maps.Clone(m1)
	m2["key"] = 100
	fmt.Println(m1["key"])
	fmt.Println(m2["key"])

	m3 := map[string][]int{
		"key": {1, 2, 3},
	}
	m4 := maps.Clone(m3)
	fmt.Println(m4["key"][0])
	m4["key"][0] = 100
	fmt.Println(m3["key"][0])
	fmt.Println(m4["key"][0])

}

func Collect ¶

func Collect[K comparable, V any](seq iter.Seq2[K, V]) map[K]V

Collect collects key-value pairs from seq into a new map and returns it.

▸ Example

▾ Example

package main

import (
	"fmt"
	"maps"
	"slices"
)

func main() {
	s1 := []string{"zero", "one", "two", "three"}
	m1 := maps.Collect(slices.All(s1))
	fmt.Println("m1 is:", m1)
}

m1 is: map[0:zero 1:one 2:two 3:three]

func Copy ¶

func Copy[M1 ~map[K]V, M2 ~map[K]V, K comparable, V any](dst M1, src M2)

Copy copies all key/value pairs in src adding them to dst. When a key in src is already present in dst, the value in dst will be overwritten by the value associated with the key in src.

▸ Example

▾ Example

package main

import (
	"fmt"
	"maps"
)

func main() {
	m1 := map[string]int{
		"one": 1,
		"two": 2,
	}
	m2 := map[string]int{
		"one": 10,
	}

	maps.Copy(m2, m1)
	fmt.Println("m2 is:", m2)

	m2["one"] = 100
	fmt.Println("m1 is:", m1)
	fmt.Println("m2 is:", m2)

	m3 := map[string][]int{
		"one": {1, 2, 3},
		"two": {4, 5, 6},
	}
	m4 := map[string][]int{
		"one": {7, 8, 9},
	}

	maps.Copy(m4, m3)
	fmt.Println("m4 is:", m4)

	m4["one"][0] = 100
	fmt.Println("m3 is:", m3)
	fmt.Println("m4 is:", m4)

}

m2 is: map[one:1 two:2]
m1 is: map[one:1 two:2]
m2 is: map[one:100 two:2]
m4 is: map[one:[1 2 3] two:[4 5 6]]
m3 is: map[one:[100 2 3] two:[4 5 6]]
m4 is: map[one:[100 2 3] two:[4 5 6]]

func DeleteFunc ¶

func DeleteFunc[M ~map[K]V, K comparable, V any](m M, del func(K, V) bool)

DeleteFunc deletes any key/value pairs from m for which del returns true.

▸ Example

▾ Example

package main

import (
	"fmt"
	"maps"
)

func main() {
	m := map[string]int{
		"one":   1,
		"two":   2,
		"three": 3,
		"four":  4,
	}
	maps.DeleteFunc(m, func(k string, v int) bool {
		return v%2 != 0 // delete odd values
	})
	fmt.Println(m)
}

map[four:4 two:2]

func Equal ¶

func Equal[M1, M2 ~map[K]V, K, V comparable](m1 M1, m2 M2) bool

Equal reports whether two maps contain the same key/value pairs. Values are compared using ==.

▸ Example

▾ Example

package main

import (
	"fmt"
	"maps"
)

func main() {
	m1 := map[int]string{
		1:    "one",
		10:   "Ten",
		1000: "THOUSAND",
	}
	m2 := map[int]string{
		1:    "one",
		10:   "Ten",
		1000: "THOUSAND",
	}
	m3 := map[int]string{
		1:    "one",
		10:   "ten",
		1000: "thousand",
	}

	fmt.Println(maps.Equal(m1, m2))
	fmt.Println(maps.Equal(m1, m3))
}

true
false

func EqualFunc ¶

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

EqualFunc is like Equal, but compares values using eq. Keys are still compared with ==.

▸ Example

▾ Example

package main

import (
	"fmt"
	"maps"
	"strings"
)

func main() {
	m1 := map[int]string{
		1:    "one",
		10:   "Ten",
		1000: "THOUSAND",
	}
	m2 := map[int][]byte{
		1:    []byte("One"),
		10:   []byte("Ten"),
		1000: []byte("Thousand"),
	}
	eq := maps.EqualFunc(m1, m2, func(v1 string, v2 []byte) bool {
		return strings.ToLower(v1) == strings.ToLower(string(v2))
	})
	fmt.Println(eq)
}

true

func Insert ¶

func Insert[Map ~map[K]V, K comparable, V any](m Map, seq iter.Seq2[K, V])

Insert adds the key-value pairs from seq to m. If a key in seq already exists in m, its value will be overwritten.

▸ Example

▾ Example

package main

import (
	"fmt"
	"maps"
	"slices"
)

func main() {
	m1 := map[int]string{
		1000: "THOUSAND",
	}
	s1 := []string{"zero", "one", "two", "three"}
	maps.Insert(m1, slices.All(s1))
	fmt.Println("m1 is:", m1)
}

m1 is: map[0:zero 1:one 2:two 3:three 1000:THOUSAND]

func Keys ¶

func Keys[Map ~map[K]V, K comparable, V any](m Map) iter.Seq[K]

Keys returns an iterator over keys in m. The iteration order is not specified and is not guaranteed to be the same from one call to the next.

▸ Example

▾ Example

package main

import (
	"fmt"
	"maps"
	"slices"
)

func main() {
	m1 := map[int]string{
		1:    "one",
		10:   "Ten",
		1000: "THOUSAND",
	}
	keys := slices.Sorted(maps.Keys(m1))
	fmt.Println(keys)
}

[1 10 1000]

func Values ¶

func Values[Map ~map[K]V, K comparable, V any](m Map) iter.Seq[V]

Values returns an iterator over values in m. The iteration order is not specified and is not guaranteed to be the same from one call to the next.

▸ Example

▾ Example

package main

import (
	"fmt"
	"maps"
	"slices"
)

func main() {
	m1 := map[int]string{
		1:    "one",
		10:   "Ten",
		1000: "THOUSAND",
	}
	values := slices.Sorted(maps.Values(m1))
	fmt.Println(values)
}

[THOUSAND Ten one]