A+ will have a maintenance break for a version upgrade on Thursday October 28th 2021, starting at 8:00 A.M. The site will not be available during the break. The break is expected to last for two hours, but site will be available as soon as the upgrade is complete. More information.
This course has already ended.

Luet oppimateriaalin englanninkielistä versiota. Mainitsit kuitenkin taustakyselyssä osaavasi suomea. Siksi suosittelemme, että käytät suomenkielistä versiota, joka on testatumpi ja hieman laajempi ja muutenkin mukava.

Suomenkielinen materiaali kyllä esittelee englanninkielisetkin termit. Myös suomenkielisessä materiaalissa käytetään ohjelmaprojektien koodissa englanninkielisiä nimiä kurssin alkupään johdantoesimerkkejä lukuunottamatta.

Voit vaihtaa kieltä A+:n valikon yläreunassa olevasta painikkeesta. Tai tästä: Vaihda suomeksi.

Style Guide

About This Page:

Questions Answered How can I make my program code easier to read and edit? How should I indent my Scala code; which functions should have brackets; what about lower- and upper-case letters?

Topics: Selected aspects of formatting Scala code.

Prerequisites: Much of this guide should be understandable after Week 3 of O1, but there are a few points that concern later topics.

Page unavailable in English at the moment   :-(

Due to time pressures, this page hasn’t been translated yet for the first English-language offering of O1 in Fall 2018.

We are sorry.

Fortunately, there are other resources available in English that cover essentially the same material.

We’ll try and get an English translation of this page up as soon as possible. In the meantime, read the semi-official coding conventions for Scala. If you want, you can also take a look at the Scala coding conventions recommended at PayPal, DataBricks, and Twitter.

O1 doesn’t religiously follow any of those guides, nor do we expect you to. But do try to be consistent and try to get the basics right: indent your code, use sensible variable names, etc.

Summary of Key Points

  • Good programming style makes programs easier to read and develop. One basic aspect of style is the formatting of source code so that the program text aids the human reader to understand the program.
  • A style convention specifies a particular manner of writing code: how to indent, how to name variables, etc. Different programming languages have their own style conventions; there are usually multiple alternative practices for any given language.
  • No matter which style you pick, you should apply it consistently so that you don’t put an extra burden on your reader. On the other hand, it can be okay to deviate from convention if there are reasons to do so in a particular context.
  • Links to the glossary: programming style, style convention; comment; to indent; identifier.

The Final Word

Any fool can write code that a computer can understand.
Good programmers write code that humans can understand.

—Martin Fowler



Thousands of students have given feedback that has contributed to this ebook’s design. Thank you!

Weeks 1 to 13 of the ebook, including the assignments and weekly bulletins, have been written in Finnish and translated into English by Juha Sorva.

Weeks 14 to 20 are by Otto Seppälä. That part of the ebook isn’t available during the fall term, but we’ll publish it when it’s time.

The appendices (glossary, Scala reference, FAQ, etc.) are by Juha Sorva unless otherwise specified on the page.

The automatic assessment of the assignments has been programmed by Riku Autio, Jaakko Kantojärvi, Teemu Lehtinen, Timi Seppälä, Teemu Sirkiä, and Aleksi Vartiainen.

The illustrations at the top of each chapter, and the similar drawings elsewhere in the ebook, are the work of Christina Lassheikki.

The animations that detail the execution Scala programs have been designed by Juha Sorva and Teemu Sirkiä. Teemu Sirkiä and Riku Autio have done the technical implementation, relying on Teemu’s Jsvee and Kelmu toolkits.

The other diagrams and interactive presentations in the ebook are by Juha Sorva.

The O1Library software has been developed by Aleksi Lukkarinen and Juha Sorva. Several of its key components are built upon Aleksi’s SMCL library.

The pedagogy of using tools from O1Library (such as Pic) for simple graphical programming is inspired by the textbooks How to Design Programs by Flatt, Felleisen, Findler, and Krishnamurthi and Picturing Programs by Stephen Bloch.

The course platform A+ has been created by Aalto’s LeTech research group and is largely developed by students. The current lead developer is Jaakko Kantojärvi; many other students of computer science and information networks are also active on the project.

For O1’s current teaching staff, please see Chapter 1.1.

Additional credits appear at the ends of some chapters.

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