diff options
Diffstat (limited to 'tpl/collections/symdiff.go')
-rw-r--r-- | tpl/collections/symdiff.go | 71 |
1 files changed, 71 insertions, 0 deletions
diff --git a/tpl/collections/symdiff.go b/tpl/collections/symdiff.go new file mode 100644 index 000000000..1c58257e4 --- /dev/null +++ b/tpl/collections/symdiff.go @@ -0,0 +1,71 @@ +// 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 + +} |