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

telemachus
PragProg Customers

Warnings in Python Testing With Pytest Chapter 2
Python Testing With Pytest - Chapter 2, warnings for “unregistered custom marks” While running the smoke tests in Chapter 2, I get these...
#pragprog#errata/book-python-testing-with-pytest
5 2081 1
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
simonpeter
PragProg Customers

Web Development with Clojure, Third Edition: (create-migration "guestbook") not working (page 9)
When I try the command to create a pair of migration files I get an error. user=&gt; (create-migration "guestbook") Execution error (Ill...
#errata/book-web-development-with-clojure-third-edition
5 1788 4
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
lirux
PragProg Customers

The Ray Tracer Challenge: "Computing the normal on a transformed sphere" ebook test
Hi Jamis, I think there’s an issue with a test on chapter 6. I own the ebook, version P1.0 Feb. 2019. This test doesn’t pass for me: ...
#errata/book-the-ray-tracer-challenge
10 1461 5
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 1218 1
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
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
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
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

AstonJ
General Dev>Hardware

Which keyboard do you have?
If it’s a mechanical keyboard, which switches do you have? Would you recommend it? Why? What will your next keyboard be? Pics always w...
#hardware/keyboards#sticky#mechanical-keyboards
144 9115 50
New
PragmaticBookshelf
General Dev>Learning Resources

Forge Your Future with Open Source
Free and open source software is the default choice for the technologies that run our world, and it’s built and maintained by people like...
pragprog.com
#pragprog#published-book/book-forge-your-future-with-open-source
3 5654 0
New
ohm
Science/Tech>Tech Chat

Games! Which do you play?
Which, if any, games do you play? On what platform? I just bought (and completed) Minecraft Dungeons for my Nintendo Switch. Other than ...
#games
246 6097 101
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 9554 77
New
DevotionGeo
General Dev>Code Editors

Dendron: a personal knowledge management tool on top of VSCode
/vscode#visual-studio-code
30 7372 9
New
AstonJ
General Dev>Dev Chat

Languages Without Garbage Collection
Continuing the discussion from Thinking about learning Crystal, let’s discuss - I was wondering which languages don’t GC - maybe we can c...
#garbage-collection
21 5575 7
New
rustkas
Backend>Chat

Using Regular Expressions in Erlang
Intensively researching Erlang books and additional resources on it, I have found that the topic of using Regular Expressions is either c...
/erlang#regular-expressions
91 5662 43
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 10218 1
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

Simplicity
Fight complexity and reclaim the original spirit of agility by learning to simplify how you develop software. The result: a more humane a...
pragprog.com
#pragprog#published-book/book-simplicity
10 6553 8
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