gvolpe

Shared State in pure Functional Programming

Newcomers to Functional Programming are often very confused about the proper way to share state without breaking purity and end up having a mix of pure and impure code that defeats the purpose of having pure FP code in the first place.

Reason why I decided to write up a beginner friendly guide :)

Use Case

We have a program that runs three computations at the same time and updates the internal state to keep track of the

debasishg

package net.debasishg.fin

import org.joda.time.DateTime

trait Account {
  def no: String
  def name: String
  def openedOn: DateTime
  def closedOn: Option[DateTime]
}

vasanthk

System Design Cheatsheet

Picking the right architecture = Picking the right battles + Managing trade-offs

Basic Steps

1. Clarify and agree on the scope of the system

• User cases (description of sequences of events that, taken together, lead to a system doing something useful)
  • Who is going to use it?
  • How are they going to use it?

analogue

#!/usr/bin/python
# strace an existing process tree. `strace -f` only follows newly spawned
# processes which is not always what you want.
import os
import sys
import subprocess

# /proc/[pid]/task/*  == directory of threads including self
# /proc/[pid]/task/[pid]/children == child processes