| // Copyright 2019 CUE Authors |
| // |
| // 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 list contains functions for manipulating and examining lists. |
| package list |
| |
| import ( |
| "fmt" |
| "sort" |
| |
| "cuelang.org/go/cue" |
| ) |
| |
| // Drop reports the suffix of list x after the first n elements, |
| // or [] if n > len(x). |
| // |
| // For instance: |
| // |
| // Drop([1, 2, 3, 4], 2) |
| // |
| // results in |
| // |
| // [3, 4] |
| // |
| func Drop(x []cue.Value, n int) ([]cue.Value, error) { |
| if n < 0 { |
| return nil, fmt.Errorf("negative index") |
| } |
| |
| if n > len(x) { |
| return []cue.Value{}, nil |
| } |
| |
| return x[n:], nil |
| } |
| |
| // TODO: disable Flatten until we know the right default for depth. |
| // The right time to determine is at least some point after the query |
| // extensions are introduced, which may provide flatten functionality |
| // natively. |
| // |
| // // Flatten reports a flattend sequence of the list xs by expanding any elements |
| // // that are lists. |
| // // |
| // // For instance: |
| // // |
| // // Flatten([1, [[2, 3], []], [4]]) |
| // // |
| // // results in |
| // // |
| // // [1, 2, 3, 4] |
| // // |
| // func Flatten(xs cue.Value) ([]cue.Value, error) { |
| // var flatten func(cue.Value) ([]cue.Value, error) |
| // flatten = func(xs cue.Value) ([]cue.Value, error) { |
| // var res []cue.Value |
| // iter, err := xs.List() |
| // if err != nil { |
| // return nil, err |
| // } |
| // for iter.Next() { |
| // val := iter.Value() |
| // if val.Kind() == cue.ListKind { |
| // vals, err := flatten(val) |
| // if err != nil { |
| // return nil, err |
| // } |
| // res = append(res, vals...) |
| // } else { |
| // res = append(res, val) |
| // } |
| // } |
| // return res, nil |
| // } |
| // return flatten(xs) |
| // } |
| |
| // FlattenN reports a flattend sequence of the list xs by expanding any elements |
| // depth levels deep. If depth is negative all elements are expanded. |
| // |
| // For instance: |
| // |
| // FlattenN([1, [[2, 3], []], [4]], 1) |
| // |
| // results in |
| // |
| // [1, [2, 3], [], 4] |
| // |
| func FlattenN(xs cue.Value, depth int) ([]cue.Value, error) { |
| var flattenN func(cue.Value, int) ([]cue.Value, error) |
| flattenN = func(xs cue.Value, depth int) ([]cue.Value, error) { |
| var res []cue.Value |
| iter, err := xs.List() |
| if err != nil { |
| return nil, err |
| } |
| for iter.Next() { |
| val := iter.Value() |
| if val.Kind() == cue.ListKind && depth != 0 { |
| d := depth - 1 |
| values, err := flattenN(val, d) |
| if err != nil { |
| return nil, err |
| } |
| res = append(res, values...) |
| } else { |
| res = append(res, val) |
| } |
| } |
| return res, nil |
| } |
| return flattenN(xs, depth) |
| } |
| |
| // Take reports the prefix of length n of list x, or x itself if n > len(x). |
| // |
| // For instance: |
| // |
| // Take([1, 2, 3, 4], 2) |
| // |
| // results in |
| // |
| // [1, 2] |
| // |
| func Take(x []cue.Value, n int) ([]cue.Value, error) { |
| if n < 0 { |
| return nil, fmt.Errorf("negative index") |
| } |
| |
| if n > len(x) { |
| return x, nil |
| } |
| |
| return x[:n], nil |
| } |
| |
| // Slice extracts the consecutive elements from list x starting from position i |
| // up till, but not including, position j, where 0 <= i < j <= len(x). |
| // |
| // For instance: |
| // |
| // Slice([1, 2, 3, 4], 1, 3) |
| // |
| // results in |
| // |
| // [2, 3] |
| // |
| func Slice(x []cue.Value, i, j int) ([]cue.Value, error) { |
| if i < 0 { |
| return nil, fmt.Errorf("negative index") |
| } |
| |
| if i > j { |
| return nil, fmt.Errorf("invalid index: %v > %v", i, j) |
| } |
| |
| if i > len(x) { |
| return nil, fmt.Errorf("slice bounds out of range") |
| } |
| |
| if j > len(x) { |
| return nil, fmt.Errorf("slice bounds out of range") |
| } |
| |
| return x[i:j], nil |
| } |
| |
| // MinItems reports whether a has at least n items. |
| func MinItems(a []cue.Value, n int) bool { |
| return len(a) >= n |
| } |
| |
| // MaxItems reports whether a has at most n items. |
| func MaxItems(a []cue.Value, n int) bool { |
| return len(a) <= n |
| } |
| |
| // UniqueItems reports whether all elements in the list are unique. |
| func UniqueItems(a []cue.Value) bool { |
| b := []string{} |
| for _, v := range a { |
| b = append(b, fmt.Sprint(v)) |
| } |
| sort.Strings(b) |
| for i := 1; i < len(b); i++ { |
| if b[i-1] == b[i] { |
| return false |
| } |
| } |
| return true |
| } |
| |
| // Contains reports whether v is contained in a. The value must be a |
| // comparable value. |
| func Contains(a []cue.Value, v cue.Value) bool { |
| for _, w := range a { |
| if v.Equals(w) { |
| return true |
| } |
| } |
| return false |
| } |