slice.Where added

Author: solsw

enumerator.go

@@ -8,16 +8,16 @@ import (
 	"strings"
 )
 
-// Enumerator supports a simple iteration over a generic sequence. T - the type of objects to enumerate.
-// (https://docs.microsoft.com/dotnet/api/system.collections.generic.ienumerator-1)
+// Enumerator supports a simple iteration over a generic sequence. T - the type of objects to enumerate
+// (https://docs.microsoft.com/dotnet/api/system.collections.generic.ienumerator-1).
 type Enumerator[T any] interface {
 
-	// MoveNext advances the enumerator to the next element of the sequence.
-	// (https://docs.microsoft.com/dotnet/api/system.collections.ienumerator.movenext)
+	// MoveNext advances the enumerator to the next element of the sequence
+	// (https://docs.microsoft.com/dotnet/api/system.collections.ienumerator.movenext).
 	MoveNext() bool
 
-	// Current returns the element in the sequence at the current position of the enumerator.
-	// (https://docs.microsoft.com/dotnet/api/system.collections.generic.ienumerator-1.current)
+	// Current returns the element in the sequence at the current position of the enumerator
+	// (https://docs.microsoft.com/dotnet/api/system.collections.generic.ienumerator-1.current).
 	Current() T
 
 	// Reset sets the enumerator to its initial position, which is before the first element in the sequence
@@ -27,15 +27,15 @@ type Enumerator[T any] interface {
 	Reset()
 }
 
-// enrToSlice creates a slice from an Enumerator. enrToSlice returns nil if 'enr' is nil.
+// enrToSlice creates a slice from Enumerator (returns nil if 'enr' is nil).
 func enrToSlice[T any](enr Enumerator[T]) []T {
 	if enr == nil {
 		return nil
 	}
 	if slicer, ok := enr.(Slicer[T]); ok {
 		return slicer.Slice()
 	}
-	var r []T
+	r := []T{}
 	for enr.MoveNext() {
 		r = append(r, enr.Current())
 	}

go.mod

@@ -2,6 +2,6 @@ module github.com/solsw/go2linq/v2
 
 go 1.18
 
-require golang.org/x/sync v0.0.0-20220601150217-0de741cfad7f
+require golang.org/x/sync v0.0.0-20220929204114-8fcdb60fdcc0
 
-require golang.org/x/exp v0.0.0-20220613132600-b0d781184e0d
+require golang.org/x/exp v0.0.0-20221002003631-540bb7301a08

go.sum

@@ -1,4 +1,4 @@
-golang.org/x/exp v0.0.0-20220613132600-b0d781184e0d h1:vtUKgx8dahOomfFzLREU8nSv25YHnTgLBn4rDnWZdU0=
-golang.org/x/exp v0.0.0-20220613132600-b0d781184e0d/go.mod h1:Kr81I6Kryrl9sr8s2FK3vxD90NdsKWRuOIl2O4CvYbA=
-golang.org/x/sync v0.0.0-20220601150217-0de741cfad7f h1:Ax0t5p6N38Ga0dThY21weqDEyz2oklo4IvDkpigvkD8=
-golang.org/x/sync v0.0.0-20220601150217-0de741cfad7f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/exp v0.0.0-20221002003631-540bb7301a08 h1:LtBIgSqNhkuC9gA3BFjGy5obHQT1lnmNsMDFSqWzQ5w=
+golang.org/x/exp v0.0.0-20221002003631-540bb7301a08/go.mod h1:cyybsKvd6eL0RnXn6p/Grxp8F5bW7iYuBgsNCOHpMYE=
+golang.org/x/sync v0.0.0-20220929204114-8fcdb60fdcc0 h1:cu5kTvlzcw1Q5S9f5ip1/cpiB4nXvw1XYzFPGgzLUOY=
+golang.org/x/sync v0.0.0-20220929204114-8fcdb60fdcc0/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=

slice/go_test.bat

@@ -0,0 +1 @@
+go test

slice/where.go

@@ -0,0 +1,27 @@
+//go:build go1.18
+
+package slice
+
+import (
+	"github.com/solsw/go2linq/v2"
+)
+
+// Where filters a slice of T based on a predicate.
+// If 'source' is nil, nil is returned.
+// If 'source' is empty, new empty slice is returned.
+func Where[T any](source []T, predicate func(T) bool) ([]T, error) {
+	if source == nil {
+		return nil, nil
+	}
+	if len(source) == 0 {
+		return []T{}, nil
+	}
+	en, err := go2linq.Where(
+		go2linq.NewEnSlice(source...),
+		predicate,
+	)
+	if err != nil {
+		return nil, err
+	}
+	return go2linq.ToSlice(en)
+}

slice/where_test.go

@@ -0,0 +1,62 @@
+//go:build go1.18
+
+package slice
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestWhere_int(t *testing.T) {
+	type args struct {
+		source    []int
+		predicate func(int) bool
+	}
+	tests := []struct {
+		name    string
+		args    args
+		want    []int
+		wantErr bool
+	}{
+		{name: "NilSource",
+			args: args{
+				source:    nil,
+				predicate: func(i int) bool { return i > 5 },
+			},
+			want: nil,
+		},
+		{name: "EmptySource",
+			args: args{
+				source:    []int{},
+				predicate: func(i int) bool { return i > 5 },
+			},
+			want: []int{},
+		},
+		{name: "NilPredicate",
+			args: args{
+				source:    []int{1, 3, 4, 2, 8, 1},
+				predicate: nil,
+			},
+			wantErr: true,
+		},
+		{name: "SimpleFiltering",
+			args: args{
+				source:    []int{1, 3, 4, 2, 8, 1},
+				predicate: func(i int) bool { return i < 4 },
+			},
+			want: []int{1, 3, 2, 1},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := Where(tt.args.source, tt.args.predicate)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("Where() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("Where() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}