Introducing sorting algorithms in Go
Sorting Arbitrary Data
Spoiled script kiddies will be rubbing their eyes in amazement: Go's strict type system requires quite a bit of extra overhead before it will sort an array of arbitrary data. It turns out to be impossible to define a sort routine that sorts arrays with elements of a generic data type. Instead, the programmer has to explicitly specify how Go should compare and swap the elements.
Listing 7 defines a fictitious data structure Record
, which only contains an integer value as an attribute. To sort an array with elements of Record
types, the programmer has to teach Go:
- How to determine the length of the array with the data types
- How to compare two elements at the positions
i
andj
- How to swap two different entries against each other (i.e., everything a generic sort function does with its data internally while it's performing the sort)
Listing 7
sortstruct.go
01 package main 02 03 import ( 04 "fmt" 05 "sort" 06 ) 07 08 type Record struct { 09 id int 10 } 11 12 type Records []Record 13 14 func (r Records) 15 Len() int { 16 return len(r) 17 } 18 19 func (r Records) Swap(i, j int) { 20 r[i], r[j] = r[j], r[i] 21 } 22 23 func (r Records) Less(i, j int) bool { 24 return r[i].id < r[j].id 25 } 26 27 func main() { 28 data := Records{{5}, {1}, {2}, {7}, {3}} 29 sort.Sort(data) 30 fmt.Printf("%+v\n", data) 31 }
For this purpose, Listing 7 contains the Len()
, Swap()
, and Less()
functions, to each of which you need to assign a receiver as an array of Record
types (i.e., an array of the Records
type defined above). You can easily determine the length of the array with the built-in Go len()
function, so Len()
is taken care of. Two elements are swapped courtesy of Go's practical swapping syntax (a,b = b,a
), so Swap
turns out to be easy-peasy. Two elements are compared using the less-than operator (<
), as shown in line 24, which is the meat of Less()
. To have Go sort the array in place with quicksort, line 29 calls the sort.Sort()
function and passes the array with the record elements to it. The correct result, as determined by the algorithm, is shown in Listing 8.
Listing 8
Results
$ ./sortstruct [{id:1} {id:2} {id:3} {id:5} {id:7}]
It turns out that a language like Go with strict type checking requires a little more programming overhead than a scripting language that sorts strings, integers, and floats without complaining, or to which you could easily add a homemade sorting function for types you define yourself. This disadvantage is not only made up for by Go's high processing speed, but also by the fact that the compiler complains about accidental type errors – rather than just the program at run time. But, as usual, there's no free lunch.
Infos
- Knuth, Donald E. The Art of Computer Programming, Volume 3: Searching and Sorting, Addison-Wesley Professional, 1998
- Cormen, Thomas H., Charles E. Leiserson, Ronald L. Rivest, and Clifford Stein. Introduction to Algorithms, MIT Press, 2009
- Listings for this article: ftp://ftp.linux-magazine.com/pub/listings/linux-magazine.com/233/
- Counting sort: https://en.wikipedia.org/wiki/Counting_sort
- Sort functions in the Go standard library: https://golang.org/src/sort/sort.go
« Previous 1 2 3
Buy this article as PDF
(incl. VAT)
Buy Linux Magazine
Subscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters
Support Our Work
Linux Magazine content is made possible with support from readers like you. Please consider contributing when you’ve found an article to be beneficial.
News
-
Canonical Bumps LTS Support to 12 years
If you're worried that your Ubuntu LTS release won't be supported long enough to last, Canonical has a surprise for you in the form of 12 years of security coverage.
-
Fedora 40 Beta Released Soon
With the official release of Fedora 40 coming in April, it's almost time to download the beta and see what's new.
-
New Pentesting Distribution to Compete with Kali Linux
SnoopGod is now available for your testing needs
-
Juno Computers Launches Another Linux Laptop
If you're looking for a powerhouse laptop that runs Ubuntu, the Juno Computers Neptune 17 v6 should be on your radar.
-
ZorinOS 17.1 Released, Includes Improved Windows App Support
If you need or desire to run Windows applications on Linux, there's one distribution intent on making that easier for you and its new release further improves that feature.
-
Linux Market Share Surpasses 4% for the First Time
Look out Windows and macOS, Linux is on the rise and has even topped ChromeOS to become the fourth most widely used OS around the globe.
-
KDE’s Plasma 6 Officially Available
KDE’s Plasma 6.0 "Megarelease" has happened, and it's brimming with new features, polish, and performance.
-
Latest Version of Tails Unleashed
Tails 6.0 is based on Debian 12 and includes GNOME 43.
-
KDE Announces New Slimbook V with Plenty of Power and KDE’s Plasma 6
If you're a fan of KDE Plasma, you'll be thrilled to hear they've announced a new Slimbook with an AMD CPU and the latest version of KDE Plasma desktop.
-
Monthly Sponsorship Includes Early Access to elementary OS 8
If you want to get a glimpse of what's in the pipeline for elementary OS 8, just set up a monthly sponsorship to help fund its continued existence.