PragProg Customers

Real-World Event Sourcing: Incorrect definition of input and output (page 27)

dsincl12

dsincl12

Real-World Event Sourcing: Incorrect definition of input and output (page 27)

@autodidaddict

On page 27 it says the following which is misleading:

“In pure functional programming terms, input and output are considered impure, because they are side effects.”

This is not correct, input and output are themselves not impure only the side effects. So this is a bit misleading. A pure function have input and output but with no side effects.

1 comment
#errata/book-real-world-event-sourcing
0 38 1

First Post!

autodidaddict

autodidaddict

Author of Real-World Event Sourcing with Elixir

Thanks for pointing this out. I’ve clarified the input and output here as interactions with external systems, and not input to functions as parameters.

Post #2

Where Next?

View thread on forum
View Real World Event Sourcing's book portal
Post errata for this book
Post a suggestion for this book
Post a question about this book
Post a review about this book
Home PragProg Customers
#errata/book-real-world-event-sourcing
0 38 1
Last post

Popular Pragmatic Bookshelf topics Top

johnp
PragProg Customers

Python Testing with pytest - Chapter 5 example c AttributeError: 'module' object has no attribute 'config'
Running the examples in chapter 5 c under pytest 5.4.1 causes an AttributeError: ‘module’ object has no attribute ‘config’. In particula...
#errata/book-python-testing-with-pytest
5 3568 1
New
brianokken
PragProg Customers

Python Testing with pytest: pytest now requires markers to be declared (downloadable code)
Many tasks_proj/tests directories exist in chapters 2, 3, 5 that have tests that use the custom markers smoke and get, which are not decl...
#errata/book-python-testing-with-pytest
2 1376 2
New
mikecargal
PragProg Customers

Hands-on Rust: can_place logic is "inside out"
Title: Hands-On Rust (Chapter 11: prefab) Just played a couple of amulet-less games. With a bit of debugging, I believe that your can_p...
#errata/book-hands-on-rust
22 1622 20
New
Mmm
PragProg Customers

Hands-on Rust: Build depending on bracket-lib fails
Hi, build fails on: bracket-lib = “~0.8.1” when running on Mac Mini M1 Rust version 1.5.0: Compiling winit v0.22.2 error[E0308]: mi...
#question/book-hands-on-rust
1 1217 1
New
conradwt
PragProg Customers

Programming Phoenix 1.4: Chapter 11 - Extracting Rumbl and RumbleWeb (Page 237, 238, 240)
First, the code resources: Page 237: rumbl_umbrella/apps/rumbl/mix.exs Note: That this file is missing. Page 238: rumbl_umbrella/app...
#errata/book-programming-phoenix-1-4
1 1106 2
New
rmurray10127
PragProg Customers

Intuitive Python: docker run… denied error (page 2)
Title: Intuitive Python: docker run… denied error (page 2) Attempted to run the docker command in both CLI and Powershell PS C:\Users\r...
#errata/book-intuitive-python
9 1256 4
New
taguniversalmachine
PragProg Customers

Programming Phoenix LiveView: B6.0 pg 56 - current-user not set
It seems the second code snippet is missing the code to set the current_user: current_user: Accounts.get_user_by_session_token(session["...
#errata/book-programming-phoenix-liveview
0 1898 8
New
Keton
PragProg Customers

Hands-on Rust: How do I debug a call chain in Rust?
When running the program in chapter 8, “Implementing Combat”, the printout Health before attack was never printed so I assumed something ...
#question/book-hands-on-rust
2 1027 2
New
ggerico
PragProg Customers

Programming Machine Learning: some plot files are throwing error
I got this error when executing the plot files on macOS Ventura 13.0.1 with Python 3.10.8 and matplotlib 3.6.1: programming_ML/code/03_...
#question/book-programming-machine-learning
1 3049 5
New
redconfetti
PragProg Customers

Docker for Rails Developers - 'docker-machine' command deprecated (page 156)
Docker-Machine became part of the Docker Toolbox, which was deprecated in 2020, long after Docker Desktop supported Docker Engine nativel...
/book-docker-for-rails-developers#suggestion
0 896 0
New

Other popular topics Top

PragmaticBookshelf
General Dev>Learning Resources

A Common-Sense Guide to Data Structures and Algorithms, Second Edition
Algorithms and data structures are much more than abstract concepts. Mastering them enables you to write code that runs faster and more e...
pragprog.com
#pragprog/python/ruby#published-book/book-a-common-sense-guide-to-data-structures-and-algorithms-second-edition#math#algorithms/js
19 4751 5
New
AstonJ
General Dev>Dev Chat

Best chairs for developers?
What chair do you have while working… and why? Is there a ‘best’ type of chair or working position for developers?
#workspace#opinions
74 5181 41
New
dasdom
General Dev>Dev Chat

Standing Desks
No chair. I have a standing desk. This post was split into a dedicated thread from our thread about chairs :slight_smile:
#workspace#opinions
177 9043 77
New
Exadra37
Linux>Questions

What is the most minimalist Linux server distro?
I am asking for any distro that only has the bare-bones to be able to get a shell in the server and then just install the packages as we ...
#linux#servers
66 23964 24
New
AstonJ
Backend>Chat

How to install Ruby 3 with ASDF
In case anyone else is wondering why Ruby 3 doesn’t show when you do asdf list-all ruby :man_facepalming: do this first: asdf plugin-upd...
/ruby#asdf
11 5679 4
New
AstonJ
Backend>Chat

Rails console using 100% CPU in dev (fix)
If you are experiencing Rails console using 100% CPU on your dev machine, then updating your development and test gems might fix the issu...
/ruby/rails
3 3971 3
New
PragmaticBookshelf
Backend>Learning Resources

Agile Web Development with Rails 7
Rails 7 completely redefines what it means to produce fantastic user experiences and provides a way to achieve all the benefits of single...
pragprog.com
#pragprog#web-development/ruby/rails#published-book/book-agile-web-development-with-rails-7
32 5327 9
New
PragmaticBookshelf
Backend>Learning Resources

Effective Haskell
Build efficient applications that exploit the unique benefits of a pure functional language, learning from an engineer who uses Haskell t...
pragprog.com
#pragprog/haskell#published-book/book-effective-haskell
15 7817 1
New
PragmaticBookshelf
Backend>Learning Resources

Agile Web Development with Rails 8
Get the comprehensive, insider information you need for Rails 8 with the new edition of this award-winning classic. Sam Ruby @rubys ...
pragprog.com
#pragprog#web-development/ruby/rails#published-book/book-agile-web-development-with-rails-8
12 5049 7
New
AstonJ
AI>Chat

Post your DeepSeek results
Curious what kind of results others are getting, I think actually prefer the 7B model to the 32B model, not only is it faster but the qua...
/deepseek
15 2909 15
New
Back to top

Latest in Real-World Event Sourcing

Real-World Event Sourcing Portal ❯

PragProg Customers

Pragmatic Bookshelf PragProg Customers ❯

Latest on Devtalk

Devtalk ❯

We ❤️ helpful members!

We reward our most helpful members via our MOTM scheme - by giving away a whopping 25 books per year!

Member of the Month

Devtalk Sponsors

Pragmatic Bookshelf

Practical resources that improve the lives of professional developers.

Erlang Solutions

We build trusted fault-tolerant systems that scale to billions of users.

Honeybadger

Real-time error tracking, performance insights, and observability for devs.

EEF

Supporting innovation across the BEAM ecosystem.

Manning Publications

Develop your skills with books, videos, and courses.

AppSignal

Catch errors, track performance, monitor hosts and more.

WyeWorks

Enabling companies to succeed by building software people love.

Pragmatic Studio

Courses that move you from confusion to "Aha, now I get it!"

View all our sponsors ❯

Categories:

Sub Categories:

Popular Portals

Devtalk Sponsors

Pragmatic Bookshelf

Practical resources that improve the lives of professional developers.

Erlang Solutions

We build trusted fault-tolerant systems that scale to billions of users.

Honeybadger

Real-time error tracking, performance insights, and observability for devs.

EEF

Supporting innovation across the BEAM ecosystem.

Manning Publications

Develop your skills with books, videos, and courses.

AppSignal

Catch errors, track performance, monitor hosts and more.

WyeWorks

Enabling companies to succeed by building software people love.

Pragmatic Studio

Courses that move you from confusion to "Aha, now I get it!"

View all our sponsors ❯

We're in Beta

About us Mission Statement See our Roadmap