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.
First Post!
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"
Popular Pragmatic Bookshelf topics
Some minor things in the paper edition that says “3 2020” on the title page verso, not mentioned in the book’s errata online:
p. 186 But...
New
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.
...
New
A Common-Sense Guide to Data Structures and Algorithms, Second Edition by Jay Wengrow @jaywengrow
Hi,
I have the paperback version of t...
New
Dear Sophie.
I tried to do the “Authorization” exercise and have two questions:
When trying to plug in an email-service, I found the ...
New
I’m new to Rust and am using this book to learn more as well as to feed my interest in game dev. I’ve just finished the flappy dragon exa...
New
Running mix deps.get in the sensor_hub directory fails with the following error:
** (Mix) No SSH public keys found in ~/.ssh. An ssh aut...
New
In general, the book isn’t yet updated for Phoenix version 1.6. On page 18 of the book, the authors indicate that an auto generated of ro...
New
When trying to run tox in parallel as explained on page 151, I got the following error:
tox: error: argument -p/–parallel: expected one...
New
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...
New
@mfazio23
I’ve applied the changes from Chapter 5 of the book and everything builds correctly and runs. But, when I try to start a game,...
New
Other popular topics
Write Elixir tests that you can be proud of. Dive into Elixir’s test philosophy and gain mastery over the terminology and concepts that u...
New
What chair do you have while working… and why?
Is there a ‘best’ type of chair or working position for developers?
New
Curious to know which languages and frameworks you’re all thinking about learning next :upside_down_face:
Perhaps if there’s enough peop...
New
My first contact with Erlang was about 2 years ago when I used RabbitMQ, which is written in Erlang, for my job. This made me curious and...
New
I have seen the keycaps I want - they are due for a group-buy this week but won’t be delivered until October next year!!! :rofl:
The Ser...
New
Intensively researching Erlang books and additional resources on it, I have found that the topic of using Regular Expressions is either c...
New
A few weeks ago I started using Warp a terminal written in rust. Though in it’s current state of development there are a few caveats (tab...
New
Rails 7 completely redefines what it means to produce fantastic user experiences and provides a way to achieve all the benefits of single...
New
zig/http.zig at 7cf2cbb33ef34c1d211135f56d30fe23b6cacd42 · ziglang/zig.
General-purpose programming language and toolchain for maintaini...
New
Node.js v22.14.0 has been released.
Link: Release 2025-02-11, Version 22.14.0 'Jod' (LTS), @aduh95 · nodejs/node · GitHub
New
Categories:
Sub Categories:
Popular Portals
- /elixir
- /rust
- /wasm
- /ruby
- /erlang
- /phoenix
- /keyboards
- /python
- /js
- /rails
- /security
- /go
- /swift
- /vim
- /clojure
- /emacs
- /haskell
- /java
- /svelte
- /onivim
- /typescript
- /kotlin
- /c-plus-plus
- /crystal
- /tailwind
- /react
- /gleam
- /ocaml
- /flutter
- /elm
- /vscode
- /ash
- /html
- /opensuse
- /zig
- /centos
- /deepseek
- /php
- /scala
- /react-native
- /lisp
- /textmate
- /sublime-text
- /nixos
- /debian
- /agda
- /django
- /deno
- /kubuntu
- /arch-linux
- /nodejs
- /revery
- /ubuntu
- /spring
- /manjaro
- /lua
- /diversity
- /julia
- /markdown
- /c








