hugo complement 代码
文件路径：/tpl/collections/complement.go
/ 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 (
"errors"
"fmt"
"reflect"
)
/ Complement gives the elements in the last element of seqs that are not in
/ any of the others.
/ All elements of seqs must be slices or arrays of comparable types.
/
/ The reasoning behind this rather clumsy API is so we can do this in the templates:
/ {{ $c := .Pages | complement $last4 }}
func (ns *Namespace) Complement(seqs ...any) (any, error) {
if len(seqs) < 2 {
return nil, errors.New("complement needs at least two arguments")
}
universe := seqs[len(seqs)-1]
as := seqs[:len(seqs)-1]
aset, err := collectIdentities(as...)
if err != nil {
return nil, err
}
v := reflect.ValueOf(universe)
switch v.Kind() {
case reflect.Array, reflect.Slice:
sl := reflect.MakeSlice(v.Type(), 0, 0)
for i := 0; i < v.Len(); i++ {
ev, _ := indirectInterface(v.Index(i))
if _, found := aset[normalize(ev)]; !found {
sl = reflect.Append(sl, ev)
}
}
return sl.Interface(), nil
default:
return nil, fmt.Errorf("arguments to complement must be slices or arrays")
}
}