// Copyright 2011 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package sort_test
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import (
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"fmt"
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"sort"
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)
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type Person struct {
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Name string
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Age int
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}
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func (p Person) String() string {
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return fmt.Sprintf("%s: %d", p.Name, p.Age)
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}
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// ByAge implements sort.Interface for []Person based on
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// the Age field.
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type ByAge []Person
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func (a ByAge) Len() int { return len(a) }
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func (a ByAge) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
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func (a ByAge) Less(i, j int) bool { return a[i].Age < a[j].Age }
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func Example() {
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people := []Person{
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{"Bob", 31},
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{"John", 42},
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{"Michael", 17},
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{"Jenny", 26},
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}
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fmt.Println(people)
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// There are two ways to sort a slice. First, one can define
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// a set of methods for the slice type, as with ByAge, and
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// call sort.Sort. In this first example we use that technique.
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sort.Sort(ByAge(people))
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fmt.Println(people)
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// The other way is to use sort.Slice with a custom Less
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// function, which can be provided as a closure. In this
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// case no methods are needed. (And if they exist, they
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// are ignored.) Here we re-sort in reverse order: compare
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// the closure with ByAge.Less.
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sort.Slice(people, func(i, j int) bool {
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return people[i].Age > people[j].Age
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})
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fmt.Println(people)
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// Output:
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// [Bob: 31 John: 42 Michael: 17 Jenny: 26]
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// [Michael: 17 Jenny: 26 Bob: 31 John: 42]
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// [John: 42 Bob: 31 Jenny: 26 Michael: 17]
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}
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