Homework 0

Introduction

This assignment gets you started with the basic tools you will need to complete all of your homework projects. This project will ensure that you have correctly installed Scala, SBT and IntelliJ.

Problem Description

You are a student who needs to install all the tools necessary to get started in CS2340.

Solution Description

In this assignment you will set up your computer to

Scala Scripts

  1. Install Scala for system-wide use on your computer by downloading the appropriate distribution from the bottom of https://www.scala-lang.org/download/

  2. Download and install a programmer’s text editor (you can also use IntelliJ as a general text editor, but it can be awkward for quick file editing). In this course we will prmiarily use IntelliJ, but it’s important to be comfortable with general-purpose text editors too.

  3. Create a directory for your CS2340 coursework somewhere on your hard disk – we suggest cs2340.
    • You can do this on the command line by navigating to the directory you want to contain is the cs2340 folder (using the cd command).
      • Create the folder with the command mkdir cs2340.
      • Enter the new folder with the command cd cs2340.
      • Note: avoid putting spaces in file and directory names, since doing so complicates the use of some command line tools.

  4. Create a subdirectory of your cs2340 directory named hw0.

  5. On the command line, make sure you are in the hw0 folder. Enter these commands (remember that ‘$’ is the shell prompt (something like ‘C:\cs2340\hw0>’ on Windows) – don’t type the shell prompt character(s)):

     $ scalac -version > hw0-output.txt
 $ scala -version 2>> hw0-output.txt

    Please note what is happening here:

    > redirects the standard output of a program. 2> (or 2>>) redirects stderr, which is used for diagnostics (such as version strings). The first line creates the hw0-output.txt file, and the second line (with the extra >) adds more text to the file. Here is a nice discussion of the file descriptors stdin, stdout and stderr.

    What this means is that > (or 2>) will overwrite the file, so if you go back to repeat the first step, you’ll need to repeat all the other steps as well.

  6. Open your text editor and create a file in your newly created hw0 directory named NimblyBimbly.sh (on Unix/Linux) or NimblyBimbly.bat (on Windows) and enter the following Scala script:

    Unix/Linux: NimblyBimbly.sh

     #!/bin/sh
 exec scala -savecompiled "$0" "$@"
 !#
    
 for (i <- 1 to 9)
   print("\u004D\u0065\u006F\u0077 ")
 println("...")
 println("\u004D\u0065\u006F\u0077 ")

    Windows: NimblyBimbly.bat

     ::#!
 @echo off
 call scala -savecompiled %0 %*
 goto :eof
 ::!#
    
 for (i <- 1 to 9)
   print("\u004D\u0065\u006F\u0077 ")
 println("...")
 println("\u004D\u0065\u006F\u0077 ")

  7. If you’re on Unix/Linux, make the script executable by entering chmod +x NimblyBimbly.sh on the command line.

  8. On the command line, go to the directory containing your newly created script and run it by entering ./NimblyBimbly.sh on Unix/Linux or NimblyBimbly.bat on Windows. You should see some output on the console.

  9. Run the script again and add its output to hw0-output.txt by entering

    Unix/Linux:

     $ ./NimblyBimbly.sh >> hw0-output.txt

    Windows:

     C:\cs2340\hw0> NimblyBimbly.bat >> hw0-output.txt

    Don’t forget the the double arrows in >>!

  10. Examine your hw0-output.txt file to ensure that it contains the scalac version string, the scala version string, and the output of running your NimblyBimbly script.

Command-line SBT Projects

  1. Install SBT for your operating system using the instructions linked on the Getting Started with Scala and SBT on the Command Line page on docs.scala-lang.org.

  2. In your hw0 directory, run the following command sbt new scala/hello-world.g8. This pulls the ‘hello-world’ template from GitHub, prompts for project template values, and creates a starter SBT project.

  3. When prompted, name the application hello-world. This will create a project called “hello-world” in a subdirectory named hello-world.

  4. cd to the hello-world directory and examine the files and directories created by the sbt new command and do the things listed on the Getting Started with Scala and SBT on the Command Line page on docs.scala-lang.org to get familiar with SBT.

  5. Copy the first non-comment, non-blank line from hello-world/build.sbt and paste it to the end of your hw0-output.txt file.

IntelliJ SBT Projects

Note: be sure to install the Scala plugin in IntelliJ.

  1. Do the steps on the Building a Scala Project with IntelliJ and SBT page on docs.scala-lang.org with the following modifications:

    • You’ll be starting with Step 2 since you already created an SBT project outside of IntelliJ (which is how we’ll always do it).
    • In the latest IntelliJ version the menu option to import an existing project is File -> New -> Project from existing sources …
    • In the File Open dialog find the build.sbt file created in the previous section. Your File Open dialog may look something like this:
    • In the “Import Project from sbt” dialog under “Use sbt shell”, check both “for imports” and “for builds”. Your “Import Project from sbt” dialog may look something like this:

  2. You may have noticed that the scala/hello-world.g8 template creates a project that uses Scala 2.12.7 and SBT 1.2.4. During the course of a Scala project you may update your Scala version or SBT version. Here’s how to update build settings (like the Scala version) and keep IntelliJ in sync (see also JetBrain’s help page for sbt projects). Do these steps:

    • In the sbt shell execute the command scalaVersion, which tells you the version of Scala sbt is using to compile and run your project. The version should be 2.12.7.
    • Open build.sbt and update the Scala version (the value of the setting scalaVersion) to the most recent stable release (2.12.8 as of January 2019).
    • Open the sbt tool window on the right and click the refresh button in the top left corner. The SBT shell will open and show the progress of the update.

    Note: You may also want to update the SBT version of an existing project, but to do that you’re better off simply updating the SBT version in project/build.properties, deleting the .idea subdirectory (which contains the IntelliJ project), and re-importing the project from build.sbt into IntelliJ as in Step 1 above.

  3. After performing the substeps of Step 2 above, in the sbt shell execute the command scalaVersion again. Copy the command’s output (which shows the updated value for scalaVersion) and paste it to the end of your hw0-output.txt file.

Double-Check your hw0-output.txt File

At this point your `hw0-output.txt file should contain

If your hw0-output.txt file is missing any of those elements you should redo all the steps that add content to hw0-output.txt in each of the previous sections.

Turn-in Procedure

Submit your hw0-output.txt file on Canvas as an attachment. When you’re ready, double-check that you have submitted and not just saved a draft.

Verify the Success of Your Submission to Canvas

Practice safe submission! Verify that your HW files were truly submitted correctly, the upload was successful, and that your program runs with no syntax or runtime errors. It is solely your responsibility to turn in your homework and practice this safe submission safeguard. NOTE: Unlike TSquare, Canvas will not send an email indicating that your assignment has been submitted successfully. Follow the steps outlined below to ensure you have submitted correctly.