v3: Track changes in Go stdlib (#8)

* Adapt to changes in exp/slices.

* Implement in terms of new slices, maps, and cmp packages; require Go 1.21.

* Remove x/exp dependency.

* Require Go 1.21 in CI.

.github/workflows/go.yml

@@ -15,7 +15,7 @@ jobs:
     - name: Set up Go
       uses: actions/setup-go@v2
       with:
-        go-version: 1.18
+        go-version: 1.21
 
     - name: Unit tests
       run: go test -v -coverprofile=cover.out ./...

.github/workflows/golangci-lint.yml

@@ -18,7 +18,7 @@ jobs:
     steps:
       - uses: actions/setup-go@v3
         with:
-          go-version: '1.18'
+          go-version: '1.21'
       - uses: actions/checkout@v3
       - name: golangci-lint
         uses: golangci/golangci-lint-action@v3

go.mod

@@ -1,11 +1,8 @@
-module github.com/bobg/go-generics/v2
+module github.com/bobg/go-generics/v3
 
-go 1.18
+go 1.21
 
 require (
 	github.com/mattn/go-sqlite3 v1.14.12
-	golang.org/x/exp v0.0.0-20230213192124-5e25df0256eb
 	golang.org/x/sync v0.0.0-20210220032951-036812b2e83c
 )
-
-retract v2.0.0

go.sum

@@ -1,6 +1,4 @@
 github.com/mattn/go-sqlite3 v1.14.12 h1:TJ1bhYJPV44phC+IMu1u2K/i5RriLTPe+yc68XDJ1Z0=
 github.com/mattn/go-sqlite3 v1.14.12/go.mod h1:NyWgC/yNuGj7Q9rpYnZvas74GogHl5/Z4A/KQRfk6bU=
-golang.org/x/exp v0.0.0-20230213192124-5e25df0256eb h1:PaBZQdo+iSDyHT053FjUCgZQ/9uqVwPOcl7KSWhKn6w=
-golang.org/x/exp v0.0.0-20230213192124-5e25df0256eb/go.mod h1:CxIveKay+FTh1D0yPZemJVgC/95VzuuOLq5Qi4xnoYc=
 golang.org/x/sync v0.0.0-20210220032951-036812b2e83c h1:5KslGYwFpkhGh+Q16bwMP3cOontH8FOep7tGV86Y7SQ=
 golang.org/x/sync v0.0.0-20210220032951-036812b2e83c/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=

iter/example_test.go

@@ -3,7 +3,7 @@ package iter_test
 import (
 	"fmt"
 
-	"github.com/bobg/go-generics/v2/iter"
+	"github.com/bobg/go-generics/v3/iter"
 )
 
 func ExampleAccum() {

iter/n.go

@@ -1,6 +1,6 @@
 package iter
 
-import "github.com/bobg/go-generics/v2/internal"
+import "github.com/bobg/go-generics/v3/internal"
 
 // FirstN produces an iterator containing the first n elements of the input
 // (or all of the input, if there are fewer than n elements).

maps/dropin.go

@@ -1,20 +1,8 @@
 package maps
 
-import "golang.org/x/exp/maps"
+import "maps"
 
-// This file contains entrypoints for each of the functions in in golang.org/x/exp/maps.
-
-// Keys returns the keys of the map m.
-// The keys will be in an indeterminate order.
-func Keys[M ~map[K]V, K comparable, V any](m M) []K {
-	return maps.Keys(m)
-}
-
-// Values returns the values of the map m.
-// The values will be in an indeterminate order.
-func Values[M ~map[K]V, K comparable, V any](m M) []V {
-	return maps.Values(m)
-}
+// This file contains entrypoints for each of the functions in the standard Go maps package.
 
 // Equal reports whether two maps contain the same key/value pairs.
 // Values are compared using ==.
@@ -28,11 +16,6 @@ func EqualFunc[M1 ~map[K]V1, M2 ~map[K]V2, K comparable, V1, V2 any](m1 M1, m2 M
 	return maps.EqualFunc(m1, m2, eq)
 }
 
-// Clear removes all entries from m, leaving it empty.
-func Clear[M ~map[K]V, K comparable, V any](m M) {
-	maps.Clear(m)
-}
-
 // Clone returns a copy of m.  This is a shallow clone:
 // the new keys and values are set using ordinary assignment.
 func Clone[M ~map[K]V, K comparable, V any](m M) M {

maps/dropin_test.go

@@ -12,7 +12,7 @@ import (
 	"strconv"
 	"testing"
 
-	"github.com/bobg/go-generics/v2/slices"
+	"github.com/bobg/go-generics/v3/slices"
 )
 
 var m1 = map[int]int{1: 2, 2: 4, 4: 8, 8: 16}

maps/maps.go

@@ -8,7 +8,7 @@
 // in Go 1.21 (https://go.dev/doc/go1.21#maps).
 package maps
 
-import "github.com/bobg/go-generics/v2/iter"
+import "github.com/bobg/go-generics/v3/iter"
 
 // Each calls a function on each key-value pair in the given map.
 func Each[M ~map[K]V, K comparable, V any](m M, f func(K, V)) {
@@ -63,3 +63,30 @@ func InvertMulti[M ~map[K]V, K, V comparable](m M) map[V][]K {
 	}
 	return result
 }
+
+// Keys returns the keys of the map m.
+// The keys will be in an indeterminate order.
+func Keys[M ~map[K]V, K comparable, V any](m M) []K {
+	result := make([]K, 0, len(m))
+	for k := range m {
+		result = append(result, k)
+	}
+	return result
+}
+
+// Values returns the values of the map m.
+// The values will be in an indeterminate order.
+func Values[M ~map[K]V, K comparable, V any](m M) []V {
+	result := make([]V, 0, len(m))
+	for _, v := range m {
+		result = append(result, v)
+	}
+	return result
+}
+
+// Clear removes all entries from m, leaving it empty.
+func Clear[M ~map[K]V, K comparable, V any](m M) {
+	for k := range m {
+		delete(m, k)
+	}
+}

maps/maps_test.go

@@ -4,7 +4,7 @@ import (
 	"reflect"
 	"testing"
 
-	"github.com/bobg/go-generics/v2/iter"
+	"github.com/bobg/go-generics/v3/iter"
 )
 
 var (

parallel/example_test.go

@@ -5,7 +5,7 @@ import (
 	"fmt"
 	"sync"
 
-	"github.com/bobg/go-generics/v2/parallel"
+	"github.com/bobg/go-generics/v3/parallel"
 )
 
 func ExampleConsumers() {

parallel/parallel.go

@@ -8,7 +8,7 @@ import (
 
 	"golang.org/x/sync/errgroup"
 
-	"github.com/bobg/go-generics/v2/iter"
+	"github.com/bobg/go-generics/v3/iter"
 )
 
 // Error is an error type for wrapping errors returned from worker goroutines.

parallel/parallel_test.go

@@ -6,7 +6,7 @@ import (
 	"sync"
 	"testing"
 
-	"github.com/bobg/go-generics/v2/set"
+	"github.com/bobg/go-generics/v3/set"
 )
 
 func TestValues(t *testing.T) {

set/example_test.go

@@ -3,7 +3,7 @@ package set_test
 import (
 	"fmt"
 
-	"github.com/bobg/go-generics/v2/set"
+	"github.com/bobg/go-generics/v3/set"
 )
 
 func ExampleDiff() {

set/set.go

@@ -2,8 +2,8 @@
 package set
 
 import (
-	"github.com/bobg/go-generics/v2/iter"
-	"github.com/bobg/go-generics/v2/maps"
+	"github.com/bobg/go-generics/v3/iter"
+	"github.com/bobg/go-generics/v3/maps"
 )
 
 // Of is a set of elements of type T.

slices/combinatorics.go

@@ -1,7 +1,7 @@
 package slices
 
 import (
-	"github.com/bobg/go-generics/v2/iter"
+	"github.com/bobg/go-generics/v3/iter"
 )
 
 // Permutations produces an iterator over all permutations of s.

slices/combinatorics_test.go

@@ -5,7 +5,7 @@ import (
 	"reflect"
 	"testing"
 
-	"github.com/bobg/go-generics/v2/iter"
+	"github.com/bobg/go-generics/v3/iter"
 )
 
 func TestPermutations(t *testing.T) {