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slices: consistently use S ~[]E

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Make all functions use a constraint S ~[]E even if they don't return
the slice type. This makes explicitly instantiating the functions more
consistent: you don't have to remember which take ~[]E and which do not.
It also permits inferring the type when passing one of these functions
to some other function that is using a named slice type.

Fixes #60546

Change-Id: Ib3435255d0177fdbf03455ae527d08599b1ce012
Reviewed-on: https://go-review.googlesource.com/c/go/+/502955
Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@google.com>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Axel Wagner <axel.wagner.hh@googlemail.com>
Reviewed-by: Eli Bendersky <eliben@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
This commit is contained in:
Ian Lance Taylor 2023-06-13 09:46:50 -07:00 committed by Gopher Robot
parent 01b649b7ef
commit 0a48e5cbfa
4 changed files with 66 additions and 46 deletions
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40
api/go1.21.txt
View file

@ -365,35 +365,35 @@ pkg runtime, method (*Pinner) Pin(interface{}) #46787
pkg runtime, method (*Pinner) Unpin() #46787
pkg runtime, type PanicNilError struct #25448
pkg runtime, type Pinner struct #46787
pkg slices, func BinarySearch[$0 cmp.Ordered]([]$0, $0) (int, bool) #60091
pkg slices, func BinarySearchFunc[$0 interface{}, $1 interface{}]([]$0, $1, func($0, $1) int) (int, bool) #60091
pkg slices, func BinarySearch[$0 interface{ ~[]$1 }, $1 cmp.Ordered]($0, $1) (int, bool) #60091
pkg slices, func BinarySearchFunc[$0 interface{ ~[]$1 }, $1 interface{}, $2 interface{}]($0, $2, func($1, $2) int) (int, bool) #60091
pkg slices, func Clip[$0 interface{ ~[]$1 }, $1 interface{}]($0) $0 #57433
pkg slices, func Clone[$0 interface{ ~[]$1 }, $1 interface{}]($0) $0 #57433
pkg slices, func Compact[$0 interface{ ~[]$1 }, $1 comparable]($0) $0 #57433
pkg slices, func CompactFunc[$0 interface{ ~[]$1 }, $1 interface{}]($0, func($1, $1) bool) $0 #57433
pkg slices, func Compare[$0 cmp.Ordered]([]$0, []$0) int #60091
pkg slices, func CompareFunc[$0 interface{}, $1 interface{}]([]$0, []$1, func($0, $1) int) int #60091
pkg slices, func Contains[$0 comparable]([]$0, $0) bool #57433
pkg slices, func ContainsFunc[$0 interface{}]([]$0, func($0) bool) bool #57433
pkg slices, func Compare[$0 interface{ ~[]$1 }, $1 cmp.Ordered]($0, $0) int #60091
pkg slices, func CompareFunc[$0 interface{ ~[]$2 }, $1 interface{ ~[]$3 }, $2 interface{}, $3 interface{}]($0, $1, func($2, $3) int) int #60091
pkg slices, func Contains[$0 interface{ ~[]$1 }, $1 comparable]($0, $1) bool #57433
pkg slices, func ContainsFunc[$0 interface{ ~[]$1 }, $1 interface{}]($0, func($1) bool) bool #57433
pkg slices, func Delete[$0 interface{ ~[]$1 }, $1 interface{}]($0, int, int) $0 #57433
pkg slices, func DeleteFunc[$0 interface{ ~[]$1 }, $1 interface{}]($0, func($1) bool) $0 #54768
pkg slices, func Equal[$0 comparable]([]$0, []$0) bool #57433
pkg slices, func EqualFunc[$0 interface{}, $1 interface{}]([]$0, []$1, func($0, $1) bool) bool #57433
pkg slices, func Equal[$0 interface{ ~[]$1 }, $1 comparable]($0, $0) bool #57433
pkg slices, func EqualFunc[$0 interface{ ~[]$2 }, $1 interface{ ~[]$3 }, $2 interface{}, $3 interface{}]($0, $1, func($2, $3) bool) bool #57433
pkg slices, func Grow[$0 interface{ ~[]$1 }, $1 interface{}]($0, int) $0 #57433
pkg slices, func Index[$0 comparable]([]$0, $0) int #57433
pkg slices, func IndexFunc[$0 interface{}]([]$0, func($0) bool) int #57433
pkg slices, func Index[$0 interface{ ~[]$1 }, $1 comparable]($0, $1) int #57433
pkg slices, func IndexFunc[$0 interface{ ~[]$1 }, $1 interface{}]($0, func($1) bool) int #57433
pkg slices, func Insert[$0 interface{ ~[]$1 }, $1 interface{}]($0, int, ...$1) $0 #57433
pkg slices, func IsSorted[$0 cmp.Ordered]([]$0) bool #60091
pkg slices, func IsSortedFunc[$0 interface{}]([]$0, func($0, $0) int) bool #60091
pkg slices, func Max[$0 cmp.Ordered]([]$0) $0 #60091
pkg slices, func MaxFunc[$0 interface{}]([]$0, func($0, $0) int) $0 #60091
pkg slices, func Min[$0 cmp.Ordered]([]$0) $0 #60091
pkg slices, func MinFunc[$0 interface{}]([]$0, func($0, $0) int) $0 #60091
pkg slices, func IsSorted[$0 interface{ ~[]$1 }, $1 cmp.Ordered]($0) bool #60091
pkg slices, func IsSortedFunc[$0 interface{ ~[]$1 }, $1 interface{}]($0, func($1, $1) int) bool #60091
pkg slices, func Max[$0 interface{ ~[]$1 }, $1 cmp.Ordered]($0) $1 #60091
pkg slices, func MaxFunc[$0 interface{ ~[]$1 }, $1 interface{}]($0, func($1, $1) int) $1 #60091
pkg slices, func Min[$0 interface{ ~[]$1 }, $1 cmp.Ordered]($0) $1 #60091
pkg slices, func MinFunc[$0 interface{ ~[]$1 }, $1 interface{}]($0, func($1, $1) int) $1 #60091
pkg slices, func Replace[$0 interface{ ~[]$1 }, $1 interface{}]($0, int, int, ...$1) $0 #57433
pkg slices, func Reverse[$0 interface{}]([]$0) #58565
pkg slices, func Sort[$0 cmp.Ordered]([]$0) #60091
pkg slices, func SortFunc[$0 interface{}]([]$0, func($0, $0) int) #60091
pkg slices, func SortStableFunc[$0 interface{}]([]$0, func($0, $0) int) #60091
pkg slices, func Reverse[$0 interface{ ~[]$1 }, $1 interface{}]($0) #58565
pkg slices, func Sort[$0 interface{ ~[]$1 }, $1 cmp.Ordered]($0) #60091
pkg slices, func SortFunc[$0 interface{ ~[]$1 }, $1 interface{}]($0, func($1, $1) int) #60091
pkg slices, func SortStableFunc[$0 interface{ ~[]$1 }, $1 interface{}]($0, func($1, $1) int) #60091
pkg strings, func ContainsFunc(string, func(int32) bool) bool #54386
pkg sync, func OnceFunc(func()) func() #56102
pkg sync, func OnceValue[$0 interface{}](func() $0) func() $0 #56102

28
src/slices/slices.go
View file

@ -15,7 +15,7 @@ import (
// Otherwise, the elements are compared in increasing index order, and the
// comparison stops at the first unequal pair.
// Floating point NaNs are not considered equal.
func Equal[E comparable](s1, s2 []E) bool {
func Equal[S ~[]E, E comparable](s1, s2 S) bool {
if len(s1) != len(s2) {
return false
}
@ -32,7 +32,7 @@ func Equal[E comparable](s1, s2 []E) bool {
// EqualFunc returns false. Otherwise, the elements are compared in
// increasing index order, and the comparison stops at the first index
// for which eq returns false.
func EqualFunc[E1, E2 any](s1 []E1, s2 []E2, eq func(E1, E2) bool) bool {
func EqualFunc[S1 ~[]E1, S2 ~[]E2, E1, E2 any](s1 S1, s2 S2, eq func(E1, E2) bool) bool {
if len(s1) != len(s2) {
return false
}
@ -52,7 +52,7 @@ func EqualFunc[E1, E2 any](s1 []E1, s2 []E2, eq func(E1, E2) bool) bool {
// If both slices are equal until one of them ends, the shorter slice is
// considered less than the longer one.
// The result is 0 if s1 == s2, -1 if s1 < s2, and +1 if s1 > s2.
func Compare[E cmp.Ordered](s1, s2 []E) int {
func Compare[S ~[]E, E cmp.Ordered](s1, s2 S) int {
for i, v1 := range s1 {
if i >= len(s2) {
return +1
@ -73,7 +73,7 @@ func Compare[E cmp.Ordered](s1, s2 []E) int {
// The result is the first non-zero result of cmp; if cmp always
// returns 0 the result is 0 if len(s1) == len(s2), -1 if len(s1) < len(s2),
// and +1 if len(s1) > len(s2).
func CompareFunc[E1, E2 any](s1 []E1, s2 []E2, cmp func(E1, E2) int) int {
func CompareFunc[S1 ~[]E1, S2 ~[]E2, E1, E2 any](s1 S1, s2 S2, cmp func(E1, E2) int) int {
for i, v1 := range s1 {
if i >= len(s2) {
return +1
@ -91,7 +91,7 @@ func CompareFunc[E1, E2 any](s1 []E1, s2 []E2, cmp func(E1, E2) int) int {
// Index returns the index of the first occurrence of v in s,
// or -1 if not present.
func Index[E comparable](s []E, v E) int {
func Index[S ~[]E, E comparable](s S, v E) int {
for i := range s {
if v == s[i] {
return i
@ -102,7 +102,7 @@ func Index[E comparable](s []E, v E) int {
// IndexFunc returns the first index i satisfying f(s[i]),
// or -1 if none do.
func IndexFunc[E any](s []E, f func(E) bool) int {
func IndexFunc[S ~[]E, E any](s S, f func(E) bool) int {
for i := range s {
if f(s[i]) {
return i
@ -112,13 +112,13 @@ func IndexFunc[E any](s []E, f func(E) bool) int {
}
// Contains reports whether v is present in s.
func Contains[E comparable](s []E, v E) bool {
func Contains[S ~[]E, E comparable](s S, v E) bool {
return Index(s, v) >= 0
}
// ContainsFunc reports whether at least one
// element e of s satisfies f(e).
func ContainsFunc[E any](s []E, f func(E) bool) bool {
func ContainsFunc[S ~[]E, E any](s S, f func(E) bool) bool {
return IndexFunc(s, f) >= 0
}
@ -441,7 +441,7 @@ func Clip[S ~[]E, E any](s S) S {
// rotateLeft rotates b left by n spaces.
// s_final[i] = s_orig[i+r], wrapping around.
func rotateLeft[S ~[]E, E any](s S, r int) {
func rotateLeft[E any](s []E, r int) {
for r != 0 && r != len(s) {
if r*2 <= len(s) {
swap(s[:r], s[len(s)-r:])
@ -452,19 +452,19 @@ func rotateLeft[S ~[]E, E any](s S, r int) {
}
}
}
func rotateRight[S ~[]E, E any](s S, r int) {
func rotateRight[E any](s []E, r int) {
rotateLeft(s, len(s)-r)
}
// swap swaps the contents of x and y. x and y must be equal length and disjoint.
func swap[S ~[]E, E any](x, y S) {
func swap[E any](x, y []E) {
for i := 0; i < len(x); i++ {
x[i], y[i] = y[i], x[i]
}
}
// overlaps reports whether the memory ranges a[0:len(a)] and b[0:len(b)] overlap.
func overlaps[S ~[]E, E any](a, b S) bool {
func overlaps[E any](a, b []E) bool {
if len(a) == 0 || len(b) == 0 {
return false
}
@ -480,7 +480,7 @@ func overlaps[S ~[]E, E any](a, b S) bool {
// startIdx returns the index in haystack where the needle starts.
// prerequisite: the needle must be aliased entirely inside the haystack.
func startIdx[S ~[]E, E any](haystack, needle S) int {
func startIdx[E any](haystack, needle []E) int {
p := &needle[0]
for i := range haystack {
if p == &haystack[i] {
@ -492,7 +492,7 @@ func startIdx[S ~[]E, E any](haystack, needle S) int {
}
// Reverse reverses the elements of the slice in place.
func Reverse[E any](s []E) {
func Reverse[S ~[]E, E any](s S) {
for i, j := 0, len(s)-1; i < j; i, j = i+1, j-1 {
s[i], s[j] = s[j], s[i]
}

22
src/slices/slices_test.go
View file

@ -856,7 +856,7 @@ func TestReverse(t *testing.T) {
t.Errorf("Reverse(singeleton) = %v, want %v", singleton, want)
}
Reverse[string](nil)
Reverse[[]string](nil)
}
// naiveReplace is a baseline implementation to the Replace function.
@ -1053,3 +1053,23 @@ func TestReplaceGrowthRate(t *testing.T) {
t.Errorf("too many grows. got:%d want:%d", nGrow, want)
}
}
func apply[T any](v T, f func(T)) {
f(v)
}
// Test type inference with a named slice type.
func TestInference(t *testing.T) {
s1 := []int{1, 2, 3}
apply(s1, Reverse)
if want := []int{3, 2, 1}; !Equal(s1, want) {
t.Errorf("Reverse(%v) = %v, want %v", []int{1, 2, 3}, s1, want)
}
type S []int
s2 := S{4, 5, 6}
apply(s2, Reverse)
if want := (S{6, 5, 4}); !Equal(s2, want) {
t.Errorf("Reverse(%v) = %v, want %v", S{4, 5, 6}, s2, want)
}
}

22
src/slices/sort.go
View file

@ -11,7 +11,7 @@ import (
// Sort sorts a slice of any ordered type in ascending order.
// When sorting floating-point numbers, NaNs are ordered before other values.
func Sort[E cmp.Ordered](x []E) {
func Sort[S ~[]E, E cmp.Ordered](x S) {
n := len(x)
pdqsortOrdered(x, 0, n, bits.Len(uint(n)))
}
@ -23,19 +23,19 @@ func Sort[E cmp.Ordered](x []E) {
//
// SortFunc requires that cmp is a strict weak ordering.
// See https://en.wikipedia.org/wiki/Weak_ordering#Strict_weak_orderings.
func SortFunc[E any](x []E, cmp func(a, b E) int) {
func SortFunc[S ~[]E, E any](x S, cmp func(a, b E) int) {
n := len(x)
pdqsortCmpFunc(x, 0, n, bits.Len(uint(n)), cmp)
}
// SortStableFunc sorts the slice x while keeping the original order of equal
// elements, using cmp to compare elements.
func SortStableFunc[E any](x []E, cmp func(a, b E) int) {
func SortStableFunc[S ~[]E, E any](x S, cmp func(a, b E) int) {
stableCmpFunc(x, len(x), cmp)
}
// IsSorted reports whether x is sorted in ascending order.
func IsSorted[E cmp.Ordered](x []E) bool {
func IsSorted[S ~[]E, E cmp.Ordered](x S) bool {
for i := len(x) - 1; i > 0; i-- {
if cmp.Less(x[i], x[i-1]) {
return false
@ -46,7 +46,7 @@ func IsSorted[E cmp.Ordered](x []E) bool {
// IsSortedFunc reports whether x is sorted in ascending order, with cmp as the
// comparison function.
func IsSortedFunc[E any](x []E, cmp func(a, b E) int) bool {
func IsSortedFunc[S ~[]E, E any](x S, cmp func(a, b E) int) bool {
for i := len(x) - 1; i > 0; i-- {
if cmp(x[i], x[i-1]) < 0 {
return false
@ -58,7 +58,7 @@ func IsSortedFunc[E any](x []E, cmp func(a, b E) int) bool {
// Min returns the minimal value in x. It panics if x is empty.
// For floating-point numbers, Min propagates NaNs (any NaN value in x
// forces the output to be NaN).
func Min[E cmp.Ordered](x []E) E {
func Min[S ~[]E, E cmp.Ordered](x S) E {
if len(x) < 1 {
panic("slices.Min: empty list")
}
@ -71,7 +71,7 @@ func Min[E cmp.Ordered](x []E) E {
// MinFunc returns the minimal value in x, using cmp to compare elements.
// It panics if x is empty.
func MinFunc[E any](x []E, cmp func(a, b E) int) E {
func MinFunc[S ~[]E, E any](x S, cmp func(a, b E) int) E {
if len(x) < 1 {
panic("slices.MinFunc: empty list")
}
@ -87,7 +87,7 @@ func MinFunc[E any](x []E, cmp func(a, b E) int) E {
// Max returns the maximal value in x. It panics if x is empty.
// For floating-point E, Max propagates NaNs (any NaN value in x
// forces the output to be NaN).
func Max[E cmp.Ordered](x []E) E {
func Max[S ~[]E, E cmp.Ordered](x S) E {
if len(x) < 1 {
panic("slices.Max: empty list")
}
@ -100,7 +100,7 @@ func Max[E cmp.Ordered](x []E) E {
// MaxFunc returns the maximal value in x, using cmp to compare elements.
// It panics if x is empty.
func MaxFunc[E any](x []E, cmp func(a, b E) int) E {
func MaxFunc[S ~[]E, E any](x S, cmp func(a, b E) int) E {
if len(x) < 1 {
panic("slices.MaxFunc: empty list")
}
@ -117,7 +117,7 @@ func MaxFunc[E any](x []E, cmp func(a, b E) int) E {
// where target is found, or the position where target would appear in the
// sort order; it also returns a bool saying whether the target is really found
// in the slice. The slice must be sorted in increasing order.
func BinarySearch[E cmp.Ordered](x []E, target E) (int, bool) {
func BinarySearch[S ~[]E, E cmp.Ordered](x S, target E) (int, bool) {
// Inlining is faster than calling BinarySearchFunc with a lambda.
n := len(x)
// Define x[-1] < target and x[n] >= target.
@ -143,7 +143,7 @@ func BinarySearch[E cmp.Ordered](x []E, target E) (int, bool) {
// or a positive number if the slice element follows the target.
// cmp must implement the same ordering as the slice, such that if
// cmp(a, t) < 0 and cmp(b, t) >= 0, then a must precede b in the slice.
func BinarySearchFunc[E, T any](x []E, target T, cmp func(E, T) int) (int, bool) {
func BinarySearchFunc[S ~[]E, E, T any](x S, target T, cmp func(E, T) int) (int, bool) {
n := len(x)
// Define cmp(x[-1], target) < 0 and cmp(x[n], target) >= 0 .
// Invariant: cmp(x[i - 1], target) < 0, cmp(x[j], target) >= 0.