jdegoes

Applied Functional Programming with Scala - Notes

Copyright © 2016-2018 Fantasyland Institute of Learning. All rights reserved.

1. Mastering Functions

A function is a mapping from one set, called a domain, to another set, called the codomain. A function associates every element in the domain with exactly one element in the codomain. In Scala, both domain and codomain are types.

val square : Int => Int = x => x * x

pathikrit

Libraries

• Web Server: Play (framework) or http4s (library)
• Actors: akka
• Asynchronous Programming: monix (for tasks, reactors, observables, scheduler etc)
• Authentication: Silhouette
• Authorization: Deadbolt
• Command-line option parsing: case-app
• CSV Parsing: kantan.csv
• DB: doobie (for PostgreSQL)

shajra

package shajra.extn.http4s.core


import org.http4s.
  { Charset, CharsetRange, ContentCoding, EntityEncoder, HasQValue, Header,
    HeaderKey, Headers, LanguageTag, MediaRange, MediaType, QValue }
import org.http4s.headers.
  { Accept, `Accept-Encoding`, `Accept-Charset`, `Accept-Language`,
    `Content-Encoding`, `Content-Type` }
import org.http4s.util.CaseInsensitiveString

BretFisher

sudo: required #is required to use docker service in travis

language: php #can be any language, just php for example

services:
  - docker # required, but travis uses older version of docker :(

install:
  - echo "install nothing!" # put your normal pre-testing installs here

travisbrown

// Given the following ADT:

sealed trait Status
case object One extends Status
case object Two extends Status
case object Three extends Status

// They represent states. The natural progression, for this
// example, is : One -> Two -> Three

domenic

Auto-deploying built products to gh-pages with GitHub Actions

This is a set up for projects which want to check in only their source files, but have their gh-pages branch automatically updated with some compiled output every time they push.

A file below this one contains the steps for doing this with Travis CI. However, these days I recommend GitHub Actions, for the following reasons:

• It is much easier and requires less steps, because you are already authenticated with GitHub, so you don't need to share secret keys across services like you do when coordinate Travis CI and GitHub.
• It is free, with no quotas.
• Anecdotally, builds are much faster with GitHub Actions than with Travis CI, especially in terms of time spent waiting for a builder.

ndarville

"""A basic database set-up for Travis CI.

The set-up uses the 'TRAVIS' (== True) environment variable on Travis
to detect the session, and changes the default database accordingly.

Be mindful of where you place this code, as you may accidentally
assign the default database to another configuration later in your code.
"""

import os

jboner

Latency Comparison Numbers (~2012)
----------------------------------
L1 cache reference                           0.5 ns
Branch mispredict                            5   ns
L2 cache reference                           7   ns                      14x L1 cache
Mutex lock/unlock                           25   ns
Main memory reference                      100   ns                      20x L2 cache, 200x L1 cache
Compress 1K bytes with Zippy             3,000   ns        3 us
Send 1K bytes over 1 Gbps network       10,000   ns       10 us
Read 4K randomly from SSD*             150,000   ns      150 us          ~1GB/sec SSD