Engineering Orientation

engineeringorientation.md

[email protected]

Eric Kolve

Michael Schmitz

Sam Skjonsberg

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Engineering Orientation

Getting Started Wiki Page

• Technologies
  • Scala: our backend language
  • ReactJS and frontend tools
• Developer Workflow
  • Git and GitHub: source control
  • SBT: build tool

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Before We Start

• Please interrupt with questions!

• [email protected]

• We'll have a follow-up Q&A session in a week

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IDE

• You won't need one for this session.

• Most people at AI2 use IntelliJ.

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HipChat

• We'll be sharing links and discussing things in the "orientation" HipChat room.

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Languages

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A JVM-based programming language that mixes functional programing with object-oriented programming.

• Access to useful JVM components from the academic community.
• Functional constructs for rapid prototyping and productivity.

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First steps with Scala REPL

$ scala

> def fac(x: Int): Int = x match {
    case 0 => 1
    case x => x * fac(x - 1)
  }

> fac(10)

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First steps with Scala REPL

$ scala

> def fac(x: Int): Int = {
    if (x == 0) return 1
    else return fac(x - 1)
  }

> fac(10)

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First steps with Scala REPL

$ scala

> def fac(x: Int): Int = {
    if (x == 0) 1
    else fac(x - 1)
  }

> fac(10)

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Creating a simple Scala application

Create a folder "hello-world". Inside, add the following to build.sbt.

name := "hello"
organization := "org.allenai.hello"
scalaVersion := "2.11.5"

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Creating a simple Scala application

Now make a file src/main/scala/org/allenai/hello/Hello.scala and enter:

package org.allenai.hello

object Hello {
  def main(args: Array[String]): Unit = {
    println("hello")
  }
}

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Creating a simple Scala application

Now make a file src/main/scala/org/allenai/hello/Hello.scala and enter:

package org.allenai.hello

object Hello extends App {
  println("hello")
}

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Creating a simple Scala application

In the directory hello-world:

$ sbt run

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Adding dependencies

Add the following to your build.sbt:

libraryDependencies ++= Seq(
  "com.github.rodneykinney" %% "quisp" % "0.5.0"
)

// %% for Scala dependencies
// % for Java dependencies

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A slightly more complex Scala application

import quisp.Plot._
 
object Main extends App {
  val primes = Stream.from(2).filter { n =>
    (2 until n).forall(m => n % m != 0)
  }
  println(primes.take(10))
  val pi = Iterator.from(0).map { x =>
    primes.takeWhile(p => p < x).size
  }
  val chart = line(pi.take(100).toSeq)
  chart.title.text("Prime Counting Function")
}

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Scala Resources

• Primary Recommendations

• Programming in Scala, 2nd Edition (copies in Jake's office)

• Twitter Scala School

• We have many more resources

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ReactJS and the Frontend Stack

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Developer Workflow

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• Distributed version-control system
  • Each "clone" has complete version history
  • Fast because most operations use local disk
  • Stable because everyone has a complete copy

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Git Basics

• git clone: create a local copy of a respository
• git checkout -b branch: create a branch named branch and switch to it
• git add file: add a file to "the index"
• git commit: commits changes in index
• git push: push changes to the repository we cloned

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GitHub

• A cloud host for Git repositories
  • We don't need a central Git repository, but it's convenient
• A UI for Git operations
• Additional mechanisms for code sharing
  • Forks
  • Pull requests

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• An interactive, parallelizable build tool

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Running an existing Scala application

$ mkdir -p github/allenai
$ cd github/allenai
$ git clone [email protected]:username/aristo.git
$ cd aristo
$ sbt
> projects
> project frontend
> reStart

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Common SBT Commands

For more details, check out the SBT Cheat Sheet

• clean
• compile
• run and run-main
• reStart and reStop
• ~compile

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Developing a new feature

$ git checkout -b new-feature
$ vim frontend/public/index.html
$ git grep "Answering Science Questions"
$ vim frontend/webapp/app/state-views/application.html
$ sbt 'project frontend' run

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Developing a new feature

git add frontend/webapp/app/state-views/application.html
git commit -m "Rewording the Aristo frontend tagline."
git push origin new-feature

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Developing a new feature

• Create a pull request
• Assign a reviewer (your mentor is an obvious choice)
• Wait for Shippable to succeed

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Sample Project

Write a CLI that runs a sentence through the Nlp Stack Part-of-Speech tagger and prints the results. Write the code in a fork of the interns repo. When you are done, create a pull request and code review your solution with a peer.

Bonus: create a web application performs the above behavior in a web UI.