slices: add reduce functions

Author: Sypheos

go.mod

@@ -1,6 +1,6 @@
 module github.com/upfluence/pkg
 
-go 1.21
+go 1.23
 
 require (
 	github.com/Microsoft/go-winio v0.4.14 // indirect
@@ -34,7 +34,7 @@ require (
 	github.com/upfluence/stats v0.1.4
 	github.com/upfluence/thrift v2.4.4+incompatible
 	golang.org/x/oauth2 v0.19.0
-	golang.org/x/sync v0.4.0
+	golang.org/x/sync v0.8.0
 	golang.org/x/term v0.13.0
 	golang.org/x/text v0.13.0
 	golang.org/x/time v0.3.0
@@ -57,6 +57,7 @@ require (
 	go.uber.org/atomic v1.6.0 // indirect
 	go.uber.org/multierr v1.5.0 // indirect
 	golang.org/x/crypto v0.14.0 // indirect
+	golang.org/x/exp v0.0.0-20240909161429-701f63a606c0 // indirect
 	golang.org/x/sys v0.13.0 // indirect
 	google.golang.org/protobuf v1.31.0 // indirect
 	gopkg.in/inf.v0 v0.9.1 // indirect

go.sum

@@ -513,6 +513,8 @@ golang.org/x/crypto v0.0.0-20200622213623-75b288015ac9/go.mod h1:LzIPMQfyMNhhGPh
 golang.org/x/crypto v0.14.0 h1:wBqGXzWJW6m1XrIKlAH0Hs1JJ7+9KBwnIO8v66Q9cHc=
 golang.org/x/crypto v0.14.0/go.mod h1:MVFd36DqK4CsrnJYDkBA3VC4m2GkXAM0PvzMCn4JQf4=
 golang.org/x/exp v0.0.0-20190121172915-509febef88a4/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
+golang.org/x/exp v0.0.0-20240909161429-701f63a606c0 h1:e66Fs6Z+fZTbFBAxKfP3PALWBtpfqks2bwGcexMxgtk=
+golang.org/x/exp v0.0.0-20240909161429-701f63a606c0/go.mod h1:2TbTHSBQa924w8M6Xs1QcRcFwyucIwBGpK1p2f1YFFY=
 golang.org/x/lint v0.0.0-20181026193005-c67002cb31c3/go.mod h1:UVdnD1Gm6xHRNCYTkRU2/jEulfH38KcIWyp/GAMgvoE=
 golang.org/x/lint v0.0.0-20190227174305-5b3e6a55c961/go.mod h1:wehouNa3lNwaWXcvxsM5YxQ5yQlVC4a0KAMCusXpPoU=
 golang.org/x/lint v0.0.0-20190301231843-5614ed5bae6f/go.mod h1:UVdnD1Gm6xHRNCYTkRU2/jEulfH38KcIWyp/GAMgvoE=
@@ -560,6 +562,7 @@ golang.org/x/sync v0.0.0-20190911185100-cd5d95a43a6e/go.mod h1:RxMgew5VJxzue5/jJ
 golang.org/x/sync v0.0.0-20201207232520-09787c993a3a/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.4.0 h1:zxkM55ReGkDlKSM+Fu41A+zmbZuaPVbGMzvvdUPznYQ=
 golang.org/x/sync v0.4.0/go.mod h1:FU7BRWz2tNW+3quACPkgCx/L+uEAv1htQ0V83Z9Rj+Y=
+golang.org/x/sync v0.8.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
 golang.org/x/sys v0.0.0-20180823144017-11551d06cbcc/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20180830151530-49385e6e1522/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20180905080454-ebe1bf3edb33/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
@@ -617,6 +620,7 @@ golang.org/x/tools v0.0.0-20191029190741-b9c20aec41a5/go.mod h1:b+2E5dAYhXwXZwtn
 golang.org/x/tools v0.0.0-20200103221440-774c71fcf114/go.mod h1:TB2adYChydJhpapKDTa4BR/hXlZSLoq2Wpct/0txZ28=
 golang.org/x/tools v0.6.0 h1:BOw41kyTf3PuCW1pVQf8+Cyg8pMlkYB1oo9iJ6D/lKM=
 golang.org/x/tools v0.6.0/go.mod h1:Xwgl3UAJ/d3gWutnCtw505GrjyAbvKui8lOU390QaIU=
+golang.org/x/tools v0.25.0 h1:oFU9pkj/iJgs+0DT+VMHrx+oBKs/LJMV+Uvg78sl+fE=
 golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=

slices/reduce.go

@@ -0,0 +1,25 @@
+package slices
+
+import "golang.org/x/exp/constraints"
+
+func ReduceWith[S ~[]E, E any, A any](s S, acc A, fn func(A, E) A) A {
+	for _, e := range s {
+		acc = fn(acc, e)
+	}
+
+	return acc
+}
+
+func Reduce[S ~[]E, E any, A any](s S, fn func(A, E) A) A {
+	var acc A
+
+	return ReduceWith(s, acc, fn)
+}
+
+type sumable interface {
+	constraints.Integer | constraints.Float | ~string
+}
+
+func Sum[T sumable](i, j T) T {
+	return i + j
+}

slices/reduce_test.go

@@ -0,0 +1,55 @@
+package slices
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestReduceWith(t *testing.T) {
+	for _, tt := range []struct {
+		slice []int
+		acc   int
+		fn    func(int, int) int
+		want  int
+	}{
+		{slice: []int{1, 2, 3}, acc: 0.0, want: 6},
+		{slice: []int{1, 2, 3}, acc: 1, fn: func(a, b int) int { return a * b }, want: 6},
+		{slice: []int{}, acc: 0, fn: func(a, b int) int { return a + b }, want: 0},
+		{slice: []int{1}, acc: 0, fn: func(a, b int) int { return a + b }, want: 1},
+	} {
+		got := ReduceWith(tt.slice, tt.acc, tt.fn)
+		assert.Equal(t, tt.want, got)
+	}
+}
+
+func TestReduce(t *testing.T) {
+	for _, tt := range []struct {
+		slice []int
+		fn    func(int, int) int
+		want  int
+	}{
+		{slice: []int{1, 2, 3}, fn: func(a, b int) int { return a + b }, want: 6},
+		{slice: []int{1, 2, 3}, fn: func(a, b int) int { return a * b }, want: 0},
+		{slice: []int{}, fn: func(a, b int) int { return a + b }, want: 0},
+		{slice: []int{1}, fn: func(a, b int) int { return a + b }, want: 1},
+	} {
+		got := Reduce(tt.slice, tt.fn)
+		assert.Equal(t, tt.want, got)
+	}
+}
+
+func TestSum(t *testing.T) {
+	t.Run("integer", func(t *testing.T) {
+		assert.Equal(t, Reduce([]int{1, 2}, Sum), 3)
+		assert.Equal(t, ReduceWith([]int{1, 2}, 22, Sum), 25)
+	})
+	t.Run("float", func(t *testing.T) {
+		assert.Equal(t, Reduce([]float64{1.1, 2.3}, Sum), 3.4)
+		assert.Equal(t, ReduceWith([]float64{1.1, 2.2}, 22.22, Sum), 25.52)
+	})
+	t.Run("string", func(t *testing.T) {
+		assert.Equal(t, Reduce([]string{"foo", "bar"}, Sum), "foobar")
+		assert.Equal(t, ReduceWith([]string{"foo", "bar"}, "buz", Sum), "buzfoobar")
+	})
+}