introprog-scalalib

This is a library with Scala utilities for Computer Science teaching. The library is maintained by Björn Regnell at Lund University, Sweden. Contributions are welcome!

• The api documentation is available here: http://cs.lth.se/pgk/api/

• You can find code examples here: src/main/scala/introprog/examples

This repo is used in this course (in Swedish): http://cs.lth.se/pgk with course material published as free open source here: https://github.com/lunduniversity/introprog

How to use introprog-scalalib

Getting started using scala from the command line

You need to have Scala installed using version 3.5.2 or later.

You can start the Scala REPL in the current directory with introprog directly available to play with using this command in a terminal window:

scala repl . --dep se.lth.cs::introprog:1.4.0

You can then open a drawing window like so:

scala> val w = introprog.PixelWindow()
val w: introprog.PixelWindow = introprog.PixelWindow@34f60be9

scala> w.drawText("Hello introprog.PixelWindow!", x = 100, y = 100)

If you want to use introprog in your program, add these magic comment lines starting with //> in the beginning of your Scala 3 file (update the version number after //> using scala to the latest release):

//> using scala 3.5.2
//> using dep se.lth.cs::introprog:1.3.1

You can then run your code with scala run . (note the ending dot, meaning "current dir")

If your program looks like this:

//> using scala 3.5.2
//> using dep se.lth.cs::introprog:1.4.0

@main def run = 
  val w = introprog.PixelWindow()
  w.drawText("Hello introprog.PixelWindow!", x = 100, y = 100)

You should see green text in a new window after executing:

scala-cli run .

See: api documentation for PixelWindow for more things you can do with a PixelWindow.

You can also give the introprog dependency directly at the command line, instead of the using dep directive:

scala-cli run . --dep se.lth.cs::introprog:1.4.0

Getting started using sbt

If you use the Scala Build Tool, version 1.6 or later then put this text in a file called build.sbt

scalaVersion := "3.5.2"
libraryDependencies += "se.lth.cs" %% "introprog" % "1.4.0"

When you run sbt in terminal the introprog package is automatically downloaded and made available on your classpath. You can do things like:

> sbt
sbt> console
scala> val w = new introprog.PixelWindow()
scala> w.fill(100,100,100,100,java.awt.Color.red)

See: api documentation for PixelWindow

Older Scala versions

If you want to use Scala 2.13 with 2.13.5 or later then use these special settings in build.sbt, esp. note that you should use version 1.1.5 of introprog:

scalaVersion := "2.13.8" //2.13.5 or any later 2.13 version
scalacOptions += "-Ytasty-reader"
libraryDependencies += 
  ("se.lth.cs" %% "introprog" % "1.1.5").cross(CrossVersion.for2_13Use3)

For Scala 2.12.x and 2.13.4 and older you need to use version 1.1.4 of introprog or older.

Manual download

Download the latest jar-file from here:

• Github releases: https://github.com/lunduniversity/introprog-scalalib/releases
• Scaladex: https://index.scala-lang.org/lunduniversity/introprog-scalalib
• Search Maven central: https://search.maven.org/search?q=introprog
• Maven central server: https://repo1.maven.org/maven2/se/lth/cs/

Put the latest introprog jar-file in your sbt project in a subfolder called lib. In your build.sbt you only need scalaVersion := "3.0.1" without a library dependency to introprog, as sbt automatically put jars in lib on your classpath.

How to build introprog-scalalib

With sbt and git on your path type in terminal:

> git clone [email protected]:lunduniversity/introprog-scalalib.git
> cd introprog-scalalib
> sbt package

How to build and see the doc pages using a local server

Run this in linux bash terminal:

sbt doc && cd target/scala-3.3.3/api && python3 -m http.server 8080

Open Firefox and type this url in the address field:

http://localhost:8080/

Intentions and philosophy behind introprog-scalalib

This repo includes utilities to empower learners to advance from basic to intermediate levels of computer science by providing easy-to-use constructs for creating simple desktop apps in terminal and using simple 2D graphics. The utilities are implemented and exposed through an api that follows these guidelines:

• Use as simple constructs as possible.
• Follow Scala idioms with a pragmatic mix of imperative, functional and object-oriented programming.
• Don't use advanced functional programming concepts and magical implicits.
• Prefer a clean api with single-responsibility functions in simple modules.
• Prefer immutability over mutable state, Vector for sequences and case classes for data.
• Hide/avoid threading and complicated concurrency.
• Inspiration:
  • Talk by Martin Odersky: Scala the Simple Parts with slides here
  • Principle of least power blog post by Li Haoyi

Areas currently in scope of this library:

• Simple pixel-based 2D graphics for single-threaded game programming with explicit game loop.
• Simple blocking IO that hides the underlying complication of releasing resources etc.
• Simple modal GUI dialogs that block while waiting for user response.