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add MinOf + MaxOf methods
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@felix-kaestner
felix-kaestner committed Oct 24, 2022
1 parent e3a1279 commit 631d3e6
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Showing 2 changed files with 137 additions and 67 deletions.
114 changes: 75 additions & 39 deletions slices.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,15 @@ type number interface {
/* Signed */ ~int | ~int8 | ~int16 | ~int32 | ~int64 | /* Unsigned */ ~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr | /* Float */ ~float32 | ~float64 | /* Complex */ ~complex64 | ~complex128
}

// ordered is a constraint that permits any ordered type: any type
// that supports the operators < <= >= >.
// If future releases of Go add new ordered types,
// this constraint will be modified to include them.
// Based on: https://pkg.go.dev/golang.org/x/exp/constraints#Ordered
type ordered interface {
/* Signed */ ~int | ~int8 | ~int16 | ~int32 | ~int64 | /* Unsigned */ ~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr | /* Float */ ~float32 | ~float64 | /* String */ ~string
}

var (
errEmptySlice = errors.New("slices: empty slice")
errElementNotFound = errors.New("slices: no such element")
Expand All @@ -33,12 +42,12 @@ func Contains[E comparable](s []E, v E) bool {
// returning a newly allocated slice of all elements for which the
// function fn returns true.
func Filter[E any](s []E, fn func(e E) bool) []E {
n := 0
n := 0
r := make([]E, len(s))
for _, e := range s {
if fn(e) {
r[n] = e
n++
n++
}
}
return r[:n:n]
Expand Down Expand Up @@ -195,7 +204,7 @@ func Partition[E any](s []E, fn func(e E) bool) ([]E, []E) {
if fn(e) {
t[i] = e
i++
continue
continue
}
f[j] = e
j++
Expand Down Expand Up @@ -240,12 +249,12 @@ func Chunked[E any](s []E, n int) [][]E {

// Unique returns the unique elements of a slice.
func Unique[E comparable](s []E) []E {
n := 0
n := 0
r := make([]E, len(s))
for _, v := range s {
if !Contains(r[:n], v) {
r[n] = v
n++
r[n] = v
n++
}
}
return r[:n:n]
Expand All @@ -269,14 +278,14 @@ func UniqueInPlace[E comparable](s []E) []E {
// UniqueBy returns a slice containing only elements from of slice e
// having unique keys returned by the given selector function fn.
func UniqueBy[E1 any, E2 comparable](s []E1, fn func(e E1) E2) []E1 {
n := 0
n := 0
r := make([]E1, len(s))
k := make([]E2, len(s))
for _, v := range s {
if key := fn(v); !Contains(k[:n], key) {
k[n] = key
r[n] = v
n++
n++
}
}
return r[:n:n]
Expand All @@ -303,41 +312,41 @@ func UniqueByInPlace[E1 any, E2 comparable](s []E1, fn func(e E1) E2) []E1 {
// Intersect returns slice of all unique elements which are contained in
// both of the slices.
func Intersect[E comparable](s1, s2 []E) []E {
n := 0
u := Unique(s1)
r := make([]E, len(u))
for _, e := range u {
if Contains(s2, e) {
r[n] = e
n++
}
}
return r[:n:n]
n := 0
u := Unique(s1)
r := make([]E, len(u))
for _, e := range u {
if Contains(s2, e) {
r[n] = e
n++
}
}
return r[:n:n]
}

// Distinct returns a slice of all unique elements which are only contained in
// on of the slices
func Distinct[E comparable](s1, s2 []E) []E {
n := 0
u1 := Unique(s1)
u2 := Unique(s2)
r := make([]E, len(u1) + len(u2))
for _, e := range u1 {
if !Contains(u2, e) {
r[n] = e
n++
}
}
for _, e := range u2 {
if !Contains(u1, e) {
r[n] = e
n++
}
}
return r[:n:n]
n := 0
u1 := Unique(s1)
u2 := Unique(s2)
r := make([]E, len(u1)+len(u2))
for _, e := range u1 {
if !Contains(u2, e) {
r[n] = e
n++
}
}
for _, e := range u2 {
if !Contains(u1, e) {
r[n] = e
n++
}
}
return r[:n:n]
}

// SumOf returns the sum of all values produced by applying the function fn
// SumOf returns the max of all values produced by applying the function fn
// to each element of the slice e.
func SumOf[E any, N number](s []E, fn func(e E) N) N {
var n N
Expand All @@ -347,8 +356,35 @@ func SumOf[E any, N number](s []E, fn func(e E) N) N {
return n
}

// MinOf
// MaxOf
// MinOf returns the smallest value among the values produced by applying the
// function fn to each element in the slice s.
func MinOf[E any, N ordered](s []E, fn func(e E) N) N {
if len(s) == 0 {
panic(errEmptySlice)
}
min := fn(s[0])
for _, e := range s[1:] {
if n := fn(e); n < min {
min = n
}
}
return min
}

// MaxOf returns the largest value among the values produced by applying the
// function fn to each element in the slice s.
func MaxOf[E any, N ordered](s []E, fn func(e E) N) N {
if len(s) == 0 {
panic(errEmptySlice)
}
max := fn(s[0])
for _, e := range s[1:] {
if n := fn(e); n > max {
max = n
}
}
return max
}

// Reversed
// ReversedInPlace
// ReversedInPlace
90 changes: 62 additions & 28 deletions slices_test.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -512,9 +512,9 @@ func TestPartition(t *testing.T) {
}

for _, test := range tests {
e1, e2 := Partition(test.s, func(p *Person) bool { return p.lastname == "Hoper" })
e1, e2 := Partition(test.s, func(p *Person) bool { return p.lastname == "Hoper" })
assertEqual(t, test.e1, e1)
assertEqual(t, test.e2, e2)
assertEqual(t, test.e2, e2)
}
}

Expand Down Expand Up @@ -686,35 +686,35 @@ func TestUniqueByInPlace(t *testing.T) {
}

func TestIntersect(t *testing.T) {
tests := []struct {
s1, s2, e []int
}{
{s1: []int{}, s2: []int{}, e: []int{}},
{s1: []int{1}, s2: []int{}, e: []int{}},
{s1: []int{}, s2: []int{1}, e: []int{}},
{s1: []int{1}, s2: []int{1}, e: []int{1}},
{s1: []int{1, 2}, s2: []int{1}, e: []int{1}},
}

for _, test := range tests {
assertEqual(t, test.e, Intersect(test.s1, test.s2))
}
tests := []struct {
s1, s2, e []int
}{
{s1: []int{}, s2: []int{}, e: []int{}},
{s1: []int{1}, s2: []int{}, e: []int{}},
{s1: []int{}, s2: []int{1}, e: []int{}},
{s1: []int{1}, s2: []int{1}, e: []int{1}},
{s1: []int{1, 2}, s2: []int{1}, e: []int{1}},
}

for _, test := range tests {
assertEqual(t, test.e, Intersect(test.s1, test.s2))
}
}

func TestDistinct(t *testing.T) {
tests := []struct {
s1, s2, e []int
}{
{s1: []int{}, s2: []int{}, e: []int{}},
{s1: []int{1}, s2: []int{}, e: []int{1}},
{s1: []int{}, s2: []int{1}, e: []int{1}},
{s1: []int{1}, s2: []int{1}, e: []int{}},
{s1: []int{1, 2}, s2: []int{1}, e: []int{2}},
}

for _, test := range tests {
assertEqual(t, test.e, Distinct(test.s1, test.s2))
}
tests := []struct {
s1, s2, e []int
}{
{s1: []int{}, s2: []int{}, e: []int{}},
{s1: []int{1}, s2: []int{}, e: []int{1}},
{s1: []int{}, s2: []int{1}, e: []int{1}},
{s1: []int{1}, s2: []int{1}, e: []int{}},
{s1: []int{1, 2}, s2: []int{1}, e: []int{2}},
}

for _, test := range tests {
assertEqual(t, test.e, Distinct(test.s1, test.s2))
}
}

func TestSumOf(t *testing.T) {
Expand All @@ -732,3 +732,37 @@ func TestSumOf(t *testing.T) {
assertEqual(t, test.sum, SumOf(test.s, func(i int) int { return i }))
}
}

func TestMinOf(t *testing.T) {
tests := []struct {
s []int
min int
}{
{s: []int{1}, min: 1},
{s: []int{1, 2, 3, 4, 5}, min: 1},
}

for _, test := range tests {
assertEqual(t, test.min, MinOf(test.s, func(i int) int { return i }))
}

assertPanic(t, errEmptySlice, func() { MinOf(nil, func(i int) int { return i }) })
assertPanic(t, errEmptySlice, func() { MinOf([]int{}, func(i int) int { return i }) })
}

func TestMaxOf(t *testing.T) {
tests := []struct {
s []int
max int
}{
{s: []int{1}, max: 1},
{s: []int{1, 2, 3, 4, 5}, max: 5},
}

for _, test := range tests {
assertEqual(t, test.max, MaxOf(test.s, func(i int) int { return i }))
}

assertPanic(t, errEmptySlice, func() { MinOf(nil, func(i int) int { return i }) })
assertPanic(t, errEmptySlice, func() { MinOf([]int{}, func(i int) int { return i }) })
}

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