> For the complete documentation index, see [llms.txt](https://ineelhere.gitbook.io/code-with-go/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://ineelhere.gitbook.io/code-with-go/44-sorting-by-functions.md).

# Sorting by Functions

This Go code showcases the use of a custom sorting package named "slices" along with a comparison package "cmp" to perform sorting on slices. It demonstrates the flexibility of custom sorting by providing a comparison function.

Let's go through the code with inline comments and explanations:

```go
// Importing necessary packages.
package main

import (
	"cmp"     // Custom comparison package
	"fmt"
	"slices"  // Custom slices package for sorting
)

// The main function, where the execution of the program begins.
func main() {
	// Example with a slice of strings
	fruits := []string{"peach", "banana", "kiwi"}

	// Defining a custom comparison function for sorting based on string length
	lenCmp := func(a, b string) int {
		return cmp.Compare(len(a), len(b))
	}

	// Using the SortFunc function from the slices package to sort the string slice using the custom comparison function.
	slices.SortFunc(fruits, lenCmp)

	// Printing the sorted string slice.
	fmt.Println(fruits)

	// Example with a slice of custom type (Person)
	type Person struct {
		name string
		age  int
	}

	// Creating a slice of Person instances
	people := []Person{
		{name: "Jax", age: 37},
		{name: "TJ", age: 25},
		{name: "Alex", age: 72},
	}

	// Using the SortFunc function from the slices package to sort the Person slice using a custom comparison function.
	slices.SortFunc(people,
		func(a, b Person) int {
			return cmp.Compare(a.age, b.age)
		})

	// Printing the sorted Person slice.
	fmt.Println(people)
}
```

#### Output

```
[kiwi peach banana]
[{TJ 25} {Jax 37} {Alex 72}]
```

Now, let's discuss the `slices` package and the use of `SortFunc`:

**`slices.SortFunc(slice interface{}, less func(i, j int) int)`**

* This function takes a slice of any type (interface{}) and a custom comparison function `less`.
* The comparison function is used to determine the order of elements in the slice.
* The sorting is performed in-place, modifying the original slice.

The `main` function demonstrates the use of `SortFunc` with both a string slice (`fruits`) and a slice of custom type (`people`). It shows how to provide a custom comparison function (`lenCmp` for strings and an anonymous function for `Person` instances) to achieve sorting based on specific criteria.

Make sure that the `slices` and `cmp` packages are implemented correctly and are available in the same directory or in the Go module path for this program to work. The `import "slices"` and `import "cmp"` statements assume that there are files named `slices.go` and `cmp.go` containing the respective packages in the same directory as your main program.