PragProg Customers

Effective Haskell: Example doesn’t work (page 8)

DW_Roth

DW_Roth

Effective Haskell: Example doesn’t work (page 8)

Title: Effective Haskell - Example doesn’t work (page 8)

Middle of page 8 says: "Create a new Main.hs and copy the example below to get started.

module Main where

makeGreeting salutation person =
salutation <> " " <> person

Now load up ghci and test out…"

If I load this file into ghci (or try to compile it), I get errors: "The IO action ‘main’ is not defined in the module ‘Main’.

The text shown is not complete as it doesn’t include a main module. The reader is left to figure out why it doesn’t work.

2 comments
#errata/book-effective-haskell
1 854 2

First Post!

RebeccaSkinner

RebeccaSkinner

Author of Effective Haskell

Thanks for pointing out that bug! It will be fixed as soon as the next beta update is released.
Until then, the correct example should be:

module Main where

makeGreeting salutation person =
  salutation <> " " <> person

main = print "no salutation to show yet"
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
#errata/book-effective-haskell
1 854 2
Last post

Popular Pragmatic Bookshelf topics Top

jimschubert
PragProg Customers

Distributed Services With Go - Ch 3 index errors on Config
In Chapter 3, the source for index introduces Config on page 31, followed by more code including tests; Config isn’t introduced until pag...
#pragprog#errata/book-distributed-services-with-go
8 1316 3
New
jesse050717
PragProg Customers

Web Development with Clojure, Third Edition: Issue adding Shadow CLJS
Title: Web Development with Clojure, Third Edition, pg 116 Hi - I just started chapter 5 and I am stuck on page 116 while trying to star...
#question/book-web-development-with-clojure-third-edition
4 1199 4
New
jamis
PragProg Customers

The Ray Tracer Challenge: various errata
The following is cross-posted from the original Ray Tracer Challenge forum, from a post by garfieldnate. I’m cross-posting it so that the...
#errata/book-the-ray-tracer-challenge
4 2434 3
New
gilesdotcodes
PragProg Customers

Modern CSS with Tailwind: setting up Rails app
In case this helps anyone, I’ve had issues setting up the rails source code. Here were the solutions: In Gemfile, change gem 'rails' t...
#errata/book-modern-css-with-tailwind
3 1278 2
New
jgchristopher
PragProg Customers

Programming Phoenix LiveView: live_modal/2 instead of live_component/3 (210)
“The ProductLive.Index template calls a helper function, live_component/3, that in turn calls on the modal component. ” Excerpt From: Br...
#errata/book-programming-phoenix-liveview
3 1042 6
New
hgkjshegfskef
PragProg Customers

The Ray Tracer Challenge: cannot pass scaling test (page 69-70)
The test is as follows: Scenario: Intersecting a scaled sphere with a ray Given r ← ray(point(0, 0, -5), vector(0, 0, 1)) And s ← sphere...
#question/book-the-ray-tracer-challenge
1 1093 4
New
kevinjyh
PragProg Customers

Python Testing with pytest, Second Edition:Abou epub format
Is the book’s epub format available to read on Google Play Books?
#question/book-python-testing-with-pytest-second-edition
0 1126 3
New
taguniversalmachine
PragProg Customers

Real-Time Phoenix: ProductChannelTest - undefined function describe/2 (pg 203)
Hi, I am getting an error I cannot figure out on my test. I have what I think is the exact code from the book, other than I changed “us...
#question/book-real-time-phoenix
0 1775 6
New
tkhobbes
PragProg Customers

Modern Front-End Development for Rails - application does not start after run bin/setup (page xviii)
After some hassle, I was able to finally run bin/setup, now I have started the rails server but I get this error message right when I vis...
#errata/book-modern-front-end-development-for-rails
0 1461 5
New
davetron5000
PragProg Customers

Bug with dx/build - how to workaround until fix is up
Hello faithful readers! If you have tried to follow along in the book, you are asked to start up the dev environment via dx/build and ar...
#errata/book-ruby-on-rails-background-jobs-with-sidekiq
3 1178 19
New

Other popular topics Top

DevotionGeo
Backend>Chat

What is the reason behind Rust’s web framework, Rocket, not performing as well as expected in the Techempower benchmarks?
I know that these benchmarks might not be the exact picture of real-world scenario, but still I expect a Rust web framework performing a ...
#web-frameworks/rust
36 7463 11
New
Exadra37
Linux>Questions

AMD or Intel for Programming with Linux as the OS?
I am thinking in building or buy a desktop computer for programing, both professionally and on my free time, and my choice of OS is Linux...
#mobile#android#web-development#linux#desktop-computer#mobile-development
36 6006 10
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
DevotionGeo
Backend>Chat

Would you use Erlang now when there is Elixir?
Why, if your answer is yes?
/elixir/erlang
167 4955 52
New
AstonJ
General Dev>Code Editors

Poll: Which code editor do you use?
You might be thinking we should just ask who’s not using VSCode :joy: however there are some new additions in the space that might give V...
#community#polls/vim/emacs#code-editors/vscode#notepad/sublime-text#atom/textmate#codespaces#brackets/onivim#geany
121 5796 61
New
AstonJ
General Dev>Hardware

Keyboard thock (sound)
I’ve been hearing quite a lot of comments relating to the sound of a keyboard, with one of the most desirable of these called ‘thock’, he...
/keyboards#mechanical-keyboards
14 11197 8
New
PragmaticBookshelf
Backend>Learning Resources

Programming Phoenix LiveView
Build highly interactive applications without ever leaving Elixir, the way the experts do. Let LiveView take care of performance, scalabi...
pragprog.com
#pragprog/elixir/phoenix#published-book/book-programming-phoenix-liveview
80 9318 24
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 6600 9
New
AstonJ
macOS>Chat

How to block any website on Mac using Little Snitch
If you want a quick and easy way to block any website on your Mac using Little Snitch simply… File &gt; New Rule: And select Deny, O...
#macos#how-to#littlesnitch
5 11227 3
New
PragmaticBookshelf
Backend>Learning Resources

Programming Ruby 3.2 (5th Edition)
Programming Ruby is the most complete book on Ruby, covering both the language itself and the standard library as well as commonly used t...
twitter.com
#pragprog/ruby/rails#published-book/book-programming-ruby-3-2-5th-edition
28 8550 13
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