schmmd/engineeringorientation.md

## engineeringorientation.md

      
    Raw
  

              engineeringorientation.md
            
          
    dev-help@allenai.org

 Eric Kolve
 Michael Schmitz
 Sam Skjonsberg

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


Before We Start


Please interrupt with questions!


dev-help@allenai.org


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


IDE


You won't need one for this session.


Most people at AI2 use IntelliJ.


HipChat


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


Languages


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.


First steps with Scala REPL

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

> fac(10)

First steps with Scala REPL

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

> fac(10)

First steps with Scala REPL

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

> fac(10)

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"

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")
  }
}

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")
}

Creating a simple Scala application

In the directory hello-world:
$ sbt run

Adding dependencies

Add the following to your build.sbt:
libraryDependencies ++= Seq(
  "com.github.rodneykinney" %% "quisp" % "0.5.0"
)

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


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")
}

Scala Resources


Primary Recommendations


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


Twitter Scala School


We have many more resources


ReactJS and the Frontend Stack


Developer Workflow


Distributed version-control system

Each "clone" has complete version history
Fast because most operations use local disk
Stable because everyone has a complete copy


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


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


An interactive, parallelizable build tool


Running an existing Scala application

$ mkdir -p github/allenai
$ cd github/allenai
$ git clone git@github.com:username/aristo.git
$ cd aristo
$ sbt
> projects
> project frontend
> reStart


Common SBT Commands

For more details, check out the SBT Cheat Sheet

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


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


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


Developing a new feature


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


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.