The Lord of the Rings: an Erlang epic

Abstract

One of the first really challenging problems an Erlang novice must face is the classical process ring, which can be found around the Internet and most notably in "Erlang Programming" by Cesarini and Thompson (page 115).

Its formulation may vary, but the core of it requires the programmer to design and implement a closed ring of processes, to make them pass a given number of messages each other and then terminate gracefully.

I try here to give an in-depth analysis of the matter, to point out some of the most interesting issues of this exercise. I strongly suggest the Erlang novice to try and solve the exercise before looking at the solutions proposed here.

Linking processes

The aim of the exercise is to build a chain of processes that exchange messages. This latter specification is important since we are required to connect our processes with the only purpose of sending messages and we know that, in Erlang, a process may send a message to another process ... more


Error handling in Erlang - a primer

Abstract

This article aims to summarize Erlang error handling both in sequential and in concurrent environments. The targets of this article are novices that, like me, make their first steps into the beautiful world of Erlang. Moreover, I always find that trying to explain things makes me understand them better.

Disclaimer (for Erlang gurus): I'm a complete Erlang novice so please be indulgent with me while you read my thoughts. Corrections and suggestions are welcome!

Introduction

Recently I started studying Erlang; coming from a pure imperative background (C, C++, and Python) I have to say that Erlang has been a surprise and a joy. I did not find something so innovative since long, even if the pure functional part of the language was not totally new since it is available in Python too.

The concept of runtime system, with a support for concurrency built in the language itself, the pattern matching idea and the recursion as a way to implement loops are all ... more