PragProg Customers

Effective Haskell: Chapter 9 - Monad instance error (page 357)

billboswell

billboswell

Effective Haskell: Chapter 9 - Monad instance error (page 357)

Creating the instance of Monad Outlaw described in the text results in error:

• No instance for (Applicative Outlaw)
arising from the superclasses of an instance declaration
• In the instance declaration for ‘Monad Outlaw’

Resolved by adding Applicative instance:

Instance Applicative Outlaw where
pure = return

1 comment
/book-effective-haskell
0 292 1

First Post!

RebeccaSkinner

RebeccaSkinner

Author of Effective Haskell

Good catch, thanks. I’ll add an errata item about this.

Post #2

Where Next?

View thread on forum
View Effective Haskell'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
/book-effective-haskell
0 292 1
Last post

Popular Pragmatic Bookshelf topics Top

GilWright
PragProg Customers

Apple Game Frameworks and Technologies: Screen image may be wrong (p 13)
Working through the steps (checking that the Info,plist matches exactly), run the demo game and what appears is grey but does not fill th...
#errata/book-apple-game-frameworks-and-technologies
11 1081 5
New
AleksandrKudashkin
PragProg Customers

Modern Front-End Development for Rails: B7 no main folder in the source code (page xv)
On the page xv there is an instruction to run bin/setup from the main folder. I downloaded the source code today (12/03/21) and can’t see...
#errata/book-modern-front-end-development-for-rails
2 1452 11
New
brian-m-ops
PragProg Customers

Python Testing with pytest, Second Edition: cards pip install error (page 12)
#book-python-testing-with-pytest-second-edition Hi. Thanks for writing the book. I am just learning so this might just of been an issue ...
#errata/book-python-testing-with-pytest-second-edition
4 1191 3
New
dsmith42
PragProg Customers

iOS Unit Testing by Example: 54 Don't seem to be getting the print out on tests (Xcode 13.2)
Hey there, I’m enjoying this book and have learned a few things alredayd. However, in Chapter 4 I believe we are meant to see the “>...
#question/book-ios-unit-testing-by-example
0 1963 3
New
akraut
PragProg Customers

Programming Phoenix LiveView: Display Image Uploads (pdf p142)
The markup used to display the uploaded image results in a Phoenix.LiveView.HTMLTokenizer.ParseError error. lib/pento_web/live/product_l...
#errata/book-programming-phoenix-liveview
2 2102 9
New
jonmac
PragProg Customers

Kotlin and Android Development featuring Jetpack: allprojects should be moved to settings.gradle (page 245)
The allprojects block listed on page 245 produces the following error when syncing gradle: “org.gradle.api.GradleScriptException: A prob...
#suggestion/book-kotlin-and-android-development-featuring-jetpack
1 2304 1
New
rainforest
PragProg Customers

Real-Time Phoenix: use PubSub with implementation of Phoenix.Socket.Transport rather than channels (page 37)
Hi, I’ve got a question about the implementation of PubSub when using a Phoenix.Socket.Transport behaviour rather than channels. Before ...
#question/book-real-time-phoenix#websockets#phoenixsocket#pubsub
0 1528 3
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 1034 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 3055 5
New
bjnord
PragProg Customers

Hands-on Rust: Chapter 3: Can't get first hello to run
Hello @herbert ! Trying to get the very first “Hello, Bracket Terminal!" example to run (p. 53). I develop on an Amazon EC2 instance runn...
#question/book-hands-on-rust
0 1147 2
New

Other popular topics Top

PragmaticBookshelf
Game Dev>Learning Resources

The Ray Tracer Challenge
Brace yourself for a fun challenge: build a photorealistic 3D renderer from scratch! In just a couple of weeks, build a ray tracer that r...
pragprog.com
#pragprog#published-book/book-the-ray-tracer-challenge#algorithms
3 6115 0
New
Exadra37
General Dev>Hardware

What monitor(s) do you have for programming?
Please tell us what is your preferred monitor setup for programming(not gaming) and why you have chosen it. Does your monitor have eye p...
#monitors#coding#programming#development
227 11362 88
New
AstonJ
General Dev>Code Editors

SpaceVim vs SpaceMacs
SpaceVim seems to be gaining in features and popularity and I just wondered how it compares with SpaceMacs in 2020 - anyone have any thou...
/vim#spacevim#spacemacs/emacs#code-editors
30 4336 14
New
AstonJ
Backend>Questions

Erlang's not installing on macOS Big Sur "You are natively building Erlang/OTP for a later version of MacOSX than current version"
Just done a fresh install of macOS Big Sur and on installing Erlang I am getting: asdf install erlang 23.1.2 Configure failed. checking ...
#macos/erlang#big-sur#asdf
10 6212 8
New
PragmaticBookshelf
Community>In The Spotlight

Spotlight: Dmitry Zinoviev (Author) Interview and AMA!
Author Spotlight Dmitry Zinoviev @aqsaqal Today we’re putting our spotlight on Dmitry Zinoviev, author of Data Science Essentials in ...
#author-spotlight/python/book-complex-network-analysis-in-python/book-data-science-essentials-in-python/book-resourceful-code-reuse/book-pythonic-programming
33 5211 14
New
PragmaticBookshelf
Community>In The Spotlight

Spotlight: Jamis Buck (Author) Interview and AMA!
Author Spotlight Jamis Buck @jamis This month, we have the pleasure of spotlighting author Jamis Buck, who has written Mazes for Prog...
#author-spotlight/ruby/book-the-ray-tracer-challenge/book-mazes-for-programmers
21 6352 9
New
Help
Game Dev>Questions

Can I use Java to program a game for Nintendo switch?
I am trying to crate a game for the Nintendo switch, I wanted to use Java as I am comfortable with that programming language. Can you use...
/java#nintendo
8 4771 3
New
DevotionGeo
General Dev>Questions

Do you prefer regular mechanical keyboards or low profile mechanical keyboards and why?
I have always used antique keyboards like Cherry MX 1800 or Cherry MX 8100 and almost always have modified the switches in some way, like...
/keyboards#mechanical-keyboards
27 3877 9
New
PragmaticBookshelf
Backend>Learning Resources

Ash Framework
Explore the power of Ash Framework by modeling and building the domain for a real-world web application. Rebecca Le @sevenseacat and ...
pragprog.com
#pragprog/elixir#published-book/ash/book-ash-framework
15 7555 9
New
AstonJ
AI>Chat

How to: Run DeepSeek on Mac, Windows, and Linux!
This is a very quick guide, you just need to: Download LM Studio: https://lmstudio.ai/ Click on search Type DeepSeek, then select the o...
#macs/deepseek#guides#lm-studio
14 9328 10
New
Back to top

Latest in Effective Haskell

Effective Haskell 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.

coders51

We build reliable cloud platforms for business-critical systems.

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.

coders51

We build reliable cloud platforms for business-critical systems.

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