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Diffstat (limited to 'test/typeparam/slices.go')
-rw-r--r-- | test/typeparam/slices.go | 318 |
1 files changed, 318 insertions, 0 deletions
diff --git a/test/typeparam/slices.go b/test/typeparam/slices.go new file mode 100644 index 0000000..b24817d --- /dev/null +++ b/test/typeparam/slices.go @@ -0,0 +1,318 @@ +// run + +// Copyright 2021 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +// Package slices provides functions for basic operations on +// slices of any element type. +package main + +import ( + "fmt" + "math" + "strings" +) + +type Ordered interface { + ~int | ~int8 | ~int16 | ~int32 | ~int64 | + ~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr | + ~float32 | ~float64 | + ~string +} + +type Integer interface { + ~int | ~int8 | ~int16 | ~int32 | ~int64 | + ~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr +} + +// Max returns the maximum of two values of some ordered type. +func _Max[T Ordered](a, b T) T { + if a > b { + return a + } + return b +} + +// Min returns the minimum of two values of some ordered type. +func _Min[T Ordered](a, b T) T { + if a < b { + return a + } + return b +} + +// _Equal reports whether two slices are equal: the same length and all +// elements equal. All floating point NaNs are considered equal. +func _Equal[Elem comparable](s1, s2 []Elem) bool { + if len(s1) != len(s2) { + return false + } + for i, v1 := range s1 { + v2 := s2[i] + if v1 != v2 { + isNaN := func(f Elem) bool { return f != f } + if !isNaN(v1) || !isNaN(v2) { + return false + } + } + } + return true +} + +// _EqualFn reports whether two slices are equal using a comparison +// function on each element. +func _EqualFn[Elem any](s1, s2 []Elem, eq func(Elem, Elem) bool) bool { + if len(s1) != len(s2) { + return false + } + for i, v1 := range s1 { + v2 := s2[i] + if !eq(v1, v2) { + return false + } + } + return true +} + +// _Map turns a []Elem1 to a []Elem2 using a mapping function. +func _Map[Elem1, Elem2 any](s []Elem1, f func(Elem1) Elem2) []Elem2 { + r := make([]Elem2, len(s)) + for i, v := range s { + r[i] = f(v) + } + return r +} + +// _Reduce reduces a []Elem1 to a single value of type Elem2 using +// a reduction function. +func _Reduce[Elem1, Elem2 any](s []Elem1, initializer Elem2, f func(Elem2, Elem1) Elem2) Elem2 { + r := initializer + for _, v := range s { + r = f(r, v) + } + return r +} + +// _Filter filters values from a slice using a filter function. +func _Filter[Elem any](s []Elem, f func(Elem) bool) []Elem { + var r []Elem + for _, v := range s { + if f(v) { + r = append(r, v) + } + } + return r +} + +// _Max returns the maximum element in a slice of some ordered type. +// If the slice is empty it returns the zero value of the element type. +func _SliceMax[Elem Ordered](s []Elem) Elem { + if len(s) == 0 { + var zero Elem + return zero + } + return _Reduce(s[1:], s[0], _Max[Elem]) +} + +// _Min returns the minimum element in a slice of some ordered type. +// If the slice is empty it returns the zero value of the element type. +func _SliceMin[Elem Ordered](s []Elem) Elem { + if len(s) == 0 { + var zero Elem + return zero + } + return _Reduce(s[1:], s[0], _Min[Elem]) +} + +// _Append adds values to the end of a slice, returning a new slice. +// This is like the predeclared append function; it's an example +// of how to write it using generics. We used to write code like +// this before append was added to the language, but we had to write +// a separate copy for each type. +func _Append[T any](s []T, t ...T) []T { + lens := len(s) + tot := lens + len(t) + if tot <= cap(s) { + s = s[:tot] + } else { + news := make([]T, tot, tot+tot/2) + _Copy(news, s) + s = news + } + _Copy(s[lens:tot], t) + return s +} + +// _Copy copies values from t to s, stopping when either slice is full, +// returning the number of values copied. This is like the predeclared +// copy function; it's an example of how to write it using generics. +func _Copy[T any](s, t []T) int { + i := 0 + for ; i < len(s) && i < len(t); i++ { + s[i] = t[i] + } + return i +} + +func TestEqual() { + s1 := []int{1, 2, 3} + if !_Equal(s1, s1) { + panic(fmt.Sprintf("_Equal(%v, %v) = false, want true", s1, s1)) + } + s2 := []int{1, 2, 3} + if !_Equal(s1, s2) { + panic(fmt.Sprintf("_Equal(%v, %v) = false, want true", s1, s2)) + } + s2 = append(s2, 4) + if _Equal(s1, s2) { + panic(fmt.Sprintf("_Equal(%v, %v) = true, want false", s1, s2)) + } + + s3 := []float64{1, 2, math.NaN()} + if !_Equal(s3, s3) { + panic(fmt.Sprintf("_Equal(%v, %v) = false, want true", s3, s3)) + } + + if _Equal(s1, nil) { + panic(fmt.Sprintf("_Equal(%v, nil) = true, want false", s1)) + } + if _Equal(nil, s1) { + panic(fmt.Sprintf("_Equal(nil, %v) = true, want false", s1)) + } + if !_Equal(s1[:0], nil) { + panic(fmt.Sprintf("_Equal(%v, nil = false, want true", s1[:0])) + } +} + +func offByOne[Elem Integer](a, b Elem) bool { + return a == b+1 || a == b-1 +} + +func TestEqualFn() { + s1 := []int{1, 2, 3} + s2 := []int{2, 3, 4} + if _EqualFn(s1, s1, offByOne[int]) { + panic(fmt.Sprintf("_EqualFn(%v, %v, offByOne) = true, want false", s1, s1)) + } + if !_EqualFn(s1, s2, offByOne[int]) { + panic(fmt.Sprintf("_EqualFn(%v, %v, offByOne) = false, want true", s1, s2)) + } + + if !_EqualFn(s1[:0], nil, offByOne[int]) { + panic(fmt.Sprintf("_EqualFn(%v, nil, offByOne) = false, want true", s1[:0])) + } + + s3 := []string{"a", "b", "c"} + s4 := []string{"A", "B", "C"} + if !_EqualFn(s3, s4, strings.EqualFold) { + panic(fmt.Sprintf("_EqualFn(%v, %v, strings.EqualFold) = false, want true", s3, s4)) + } +} + +func TestMap() { + s1 := []int{1, 2, 3} + s2 := _Map(s1, func(i int) float64 { return float64(i) * 2.5 }) + if want := []float64{2.5, 5, 7.5}; !_Equal(s2, want) { + panic(fmt.Sprintf("_Map(%v, ...) = %v, want %v", s1, s2, want)) + } + + s3 := []string{"Hello", "World"} + s4 := _Map(s3, strings.ToLower) + if want := []string{"hello", "world"}; !_Equal(s4, want) { + panic(fmt.Sprintf("_Map(%v, strings.ToLower) = %v, want %v", s3, s4, want)) + } + + s5 := _Map(nil, func(i int) int { return i }) + if len(s5) != 0 { + panic(fmt.Sprintf("_Map(nil, identity) = %v, want empty slice", s5)) + } +} + +func TestReduce() { + s1 := []int{1, 2, 3} + r := _Reduce(s1, 0, func(f float64, i int) float64 { return float64(i)*2.5 + f }) + if want := 15.0; r != want { + panic(fmt.Sprintf("_Reduce(%v, 0, ...) = %v, want %v", s1, r, want)) + } + + if got := _Reduce(nil, 0, func(i, j int) int { return i + j }); got != 0 { + panic(fmt.Sprintf("_Reduce(nil, 0, add) = %v, want 0", got)) + } +} + +func TestFilter() { + s1 := []int{1, 2, 3} + s2 := _Filter(s1, func(i int) bool { return i%2 == 0 }) + if want := []int{2}; !_Equal(s2, want) { + panic(fmt.Sprintf("_Filter(%v, even) = %v, want %v", s1, s2, want)) + } + + if s3 := _Filter(s1[:0], func(i int) bool { return true }); len(s3) > 0 { + panic(fmt.Sprintf("_Filter(%v, identity) = %v, want empty slice", s1[:0], s3)) + } +} + +func TestMax() { + s1 := []int{1, 2, 3, -5} + if got, want := _SliceMax(s1), 3; got != want { + panic(fmt.Sprintf("_Max(%v) = %d, want %d", s1, got, want)) + } + + s2 := []string{"aaa", "a", "aa", "aaaa"} + if got, want := _SliceMax(s2), "aaaa"; got != want { + panic(fmt.Sprintf("_Max(%v) = %q, want %q", s2, got, want)) + } + + if got, want := _SliceMax(s2[:0]), ""; got != want { + panic(fmt.Sprintf("_Max(%v) = %q, want %q", s2[:0], got, want)) + } +} + +func TestMin() { + s1 := []int{1, 2, 3, -5} + if got, want := _SliceMin(s1), -5; got != want { + panic(fmt.Sprintf("_Min(%v) = %d, want %d", s1, got, want)) + } + + s2 := []string{"aaa", "a", "aa", "aaaa"} + if got, want := _SliceMin(s2), "a"; got != want { + panic(fmt.Sprintf("_Min(%v) = %q, want %q", s2, got, want)) + } + + if got, want := _SliceMin(s2[:0]), ""; got != want { + panic(fmt.Sprintf("_Min(%v) = %q, want %q", s2[:0], got, want)) + } +} + +func TestAppend() { + s := []int{1, 2, 3} + s = _Append(s, 4, 5, 6) + want := []int{1, 2, 3, 4, 5, 6} + if !_Equal(s, want) { + panic(fmt.Sprintf("after _Append got %v, want %v", s, want)) + } +} + +func TestCopy() { + s1 := []int{1, 2, 3} + s2 := []int{4, 5} + if got := _Copy(s1, s2); got != 2 { + panic(fmt.Sprintf("_Copy returned %d, want 2", got)) + } + want := []int{4, 5, 3} + if !_Equal(s1, want) { + panic(fmt.Sprintf("after _Copy got %v, want %v", s1, want)) + } +} +func main() { + TestEqual() + TestEqualFn() + TestMap() + TestReduce() + TestFilter() + TestMax() + TestMin() + TestAppend() + TestCopy() +} |