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

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
ianwillie
PragProg Customers

Build Websites with Hugo: Code will not run in a working Hugo setup
Hello Brian, I have some problems with running the code in your book. I like the style of the book very much and I have learnt a lot as...
#question/book-build-websites-with-hugo
0 1501 3
New
edruder
PragProg Customers

Docker for Rails Developers: Notes for Rails 6.1, Ruby 2.7.2
I thought that there might be interest in using the book with Rails 6.1 and Ruby 2.7.2. I’ll note what I needed to do differently here. ...
/book-docker-for-rails-developers
9 1177 1
New
cro
PragProg Customers

Programming Phoenix LiveView: P27, live_path confusion
I am working on the “Your Turn” for chapter one and building out the restart button talked about on page 27. It recommends looking into ...
#question/book-programming-phoenix-liveview
7 3505 14
New
Chrichton
PragProg Customers

Programming Phoenix LiveView: B03 (page 56-57) auth exercise
Dear Sophie. I tried to do the “Authorization” exercise and have two questions: When trying to plug in an email-service, I found the ...
#question/book-programming-phoenix-liveview
1 1181 3
New
leba0495
PragProg Customers

A Common-Sense Guide to Data Structures and Algorithms, Second Edition: (pg460)
Hello! Thanks for the great book. I was attempting the Trie (chap 17) exercises and for number 4 the solution provided for the autocorre...
#errata/book-a-common-sense-guide-to-data-structures-and-algorithms-second-edition
0 1157 3
New
brunogirin
PragProg Customers

Python Testing with pytest, Second Edition: unrecognized arguments error (page 122)
When I run the coverage example to report on missing lines, I get: pytest --cov=cards --report=term-missing ch7 ERROR: usage: pytest [op...
#errata/book-python-testing-with-pytest-second-edition
0 4000 1
New
brunogirin
PragProg Customers

Python Testing with pytest, Second Edition: InterpreterNotFound error when running tox (page 150)
When running tox for the first time, I got the following error: ERROR: InterpreterNotFound: python3.10 I realised that I was running ...
#errata/book-python-testing-with-pytest-second-edition
0 1306 1
New
Henrai
PragProg Customers

The Ray Tracer Challenge: Cannot get rid of acne When implement Shadows in Chapter 8.
Hi, I’m working on the Chapter 8 of the book. After I add add the point_offset, I’m still able to see acne: In the image above, I re...
#question/book-the-ray-tracer-challenge
1 1052 4
New
jwandekoken
PragProg Customers

Programming Phoenix LiveView: Live Upload Match Error
Book: Programming Phoenix LiveView, page 142 (157/378), file lib/pento_web/live/product_live/form_component.ex, in the function below: d...
#errata/book-programming-phoenix-liveview
7 1158 10
New

Other popular topics Top

Devtalk
General Dev>Dev Chat

What dev-related stuff have you been up to?
Reading something? Working on something? Planning something? Changing jobs even!? If you’re up for sharing, please let us know what you’...
#community
1045 20892 392
New
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
wolf4earth
Science/Tech>Health & Diet

How do you keep fit and healthy?
@AstonJ prompted me to open this topic after I mentioned in the lockdown thread how I started to do a lot more for my fitness. https://f...
#fitness#heath
193 4981 82
New
brentjanderson
General Dev>Hardware

Moonlander Keyboard (Mechanical) (Ergonomic) (Split) (Ortholinear)
Bought the Moonlander mechanical keyboard. Cherry Brown MX switches. Arms and wrists have been hurting enough that it’s time I did someth...
#hardware/keyboards#moonlander#mechanical-keyboards#ortholinear#ergonomic
212 17779 90
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
PragmaticBookshelf
Game Dev>Learning Resources

Hands-on Rust: Effective Learning through 2D Game Development and Play
Rust is an exciting new programming language combining the power of C with memory safety, fearless concurrency, and productivity boosters...
pragprog.com
#pragprog/rust#published-book/book-hands-on-rust
117 10879 30
New
dimitarvp
macOS>Chat

My thoughts on macOS vs Linux
Small essay with thoughts on macOS vs. Linux: I know @Exadra37 is just waiting around the corner to scream at me “I TOLD YOU SO!!!” but I...
#macos#linux
166 9730 69
New
mafinar
Community>Journals

Programming Crystal Book Club
Crystal recently reached version 1. I had been following it for awhile but never got to really learn it. Most languages I picked up out o...
/crystal/book-programming-crystal#book-club
155 4813 65
New
PragmaticBookshelf
Backend>Learning Resources

Programming WebRTC
Use WebRTC to build web applications that stream media and data in real time directly from one user to another, all in the browser. ...
pragprog.com
#pragprog#published-book/js#webrtc/book-programming-webrtc
27 6969 6
New
RobertRichards
Game Dev>Chat

Hair Salon Games for Girls Fun
Hair Salon Games for Girls Fun Girls Hair Saloon game is mainly developed for kids. This game allows users to select virtual avatars to ...
#ios#android#unity#fun
2 3556 1
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