sortGen

sortGen

A go generate-or that makes sorting arbitrary slices easier via order functions, removing the need to implement sort.Interface etc.

Simply define an order function on the slice type of interest:

// main.go
//go:generate gobin -m -run myitcv.io/sorter/cmd/sortGen

func orderByName(persons []person, i, j int) sorter.Ordered {
	return persons[i].name < persons[j].name
}

then run go generate and corresponding sort functions will have been generated for you:

// gen_main_sorter.go

func sortByName(vs []person) {
	...
}

func stableSortByName(vs []person) {
	...
}

See the example and rules below for more details.

Install

go get -u myitcv.io/sorter/cmd/sortGen

Example

Taking the example from example/main.go:

//go:generate gobin -m -run myitcv.io/sorter/cmd/sortGen -licenseFile license_header.txt

package main

import (
	"fmt"

	"myitcv.io/sorter"
)

type person struct {
	name string
	age  int
}

func main() {
	people := []person{
		person{"Sarah", 25},
		person{"Jill", 34},
		person{"Paul", 25},
	}

	fmt.Printf("Before: %v\n", people)

	sortByName(people)

	fmt.Printf("Name sorted: %v\n", people)

	m := &myStruct{}
	m.stableSortByAge(people)

	fmt.Printf("Age sorted: %v\n", people)
}

func orderByName(persons []person, i, j int) sorter.Ordered {
	return persons[i].name < persons[j].name
}

type myStruct struct {
	// some fields
}

func (m *myStruct) orderByAge(persons []person, i, j int) sorter.Ordered {
	return persons[i].age < persons[j].age
}

Then:

$ go generate
$ go build
$ ./example
Before: [{Sarah 25} {Jill 34} {Paul 25}]
Name sorted: [{Jill 34} {Paul 25} {Sarah 25}]
Age sorted: [{Paul 25} {Sarah 25} {Jill 34}]

Examine the contents of gen_main_sorter.go to see the generated functions.

Features

• Supports -licenseFile FILENAME flag which allows a file containing an uncommented license header to be included (commented) at the top of each generated file

Rules

sortGen generates sort and stable sort functions/methods according to the following simple rules:

1. The file, e.g. my_file.go, containing the order function/method must include the directive //go:generate gobin -m -run myitcv.io/sorter/cmd/sortGen
2. The order function/method name must be of the form "order*" or "Order*" (more strictly ^[oO]rder[[:word:]]+ in a regex pattern)
3. The parameters of the order function/method must be a slice type, followed by two int's
4. The return type must be myitcv.io/sorter.Ordered

The sort functions/methods generated will be of the form "sort*" or "Sort*" and "stableSort*" or "StableSort*" (following the capitalisation of the order function). They will be written to a file with a name corresponding to the input file, gen_my_file_sorter.go in the case of the file mentioned in point 1.

Notice the use of the term "function/method"; if the order function defines a receiver (i.e. it is a method) then the generated sort (and stable sort) function will use the same receiver, and hence be a method.

Implementation

The current implementation of the generator simply wraps a call to sort.Sort (or sort.Stable); this of course can be improved...

Bugs

This is only an initial proof-of-concept, probably lots of bugs and edge cases missed. Please raise issues...