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// Copyright 2018 The Hugo Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package collections
import (
"fmt"
"reflect"
"github.com/pkg/errors"
)
// SymDiff returns the symmetric difference of s1 and s2.
// Arguments must be either a slice or an array of comparable types.
func (ns *Namespace) SymDiff(s2, s1 interface{}) (interface{}, error) {
ids1, err := collectIdentities(s1)
if err != nil {
return nil, err
}
ids2, err := collectIdentities(s2)
if err != nil {
return nil, err
}
var slice reflect.Value
var sliceElemType reflect.Type
for i, s := range []interface{}{s1, s2} {
v := reflect.ValueOf(s)
switch v.Kind() {
case reflect.Array, reflect.Slice:
if i == 0 {
sliceType := v.Type()
sliceElemType = sliceType.Elem()
slice = reflect.MakeSlice(sliceType, 0, 0)
}
for i := 0; i < v.Len(); i++ {
ev, _ := indirectInterface(v.Index(i))
if !ev.Type().Comparable() {
return nil, errors.New("symdiff: elements must be comparable")
}
key := normalize(ev)
// Append if the key is not in their intersection.
if ids1[key] != ids2[key] {
v, err := convertValue(ev, sliceElemType)
if err != nil {
return nil, errors.WithMessage(err, "symdiff: failed to convert value")
}
slice = reflect.Append(slice, v)
}
}
default:
return nil, fmt.Errorf("arguments to symdiff must be slices or arrays")
}
}
return slice.Interface(), nil
}
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