
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
First Post!

RebeccaSkinner
Author of Effective Haskell
Good catch, thanks. I’ll add an errata item about this.
Popular Pragmatic Bookshelf topics

Running the examples in chapter 5 c under pytest 5.4.1 causes an AttributeError: ‘module’ object has no attribute ‘config’.
In particula...
New

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...
New

Hi! I know not the intentions behind this narrative when called, on page XI:
mount() |> handle_event() |> render()
but the correc...
New

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...
New

Title: Intuitive Python: docker run… denied error (page 2)
Attempted to run the docker command in both CLI and Powershell
PS C:\Users\r...
New

@noelrappin
Running the webpack dev server, I receive the following warning:
ERROR in tsconfig.json
TS18003: No inputs were found in c...
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

AWDWR 7, page 152, page 153:
Hello everyone,
I’m a little bit lost on the hotwire part. I didn’t fully understand it.
On page 152 @rub...
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’m following the indications of the book and arriver ad chapter 10, but the app cannot be compiled due to an error in the Bas...
New
Other popular topics

Hello Devtalk World!
Please let us know a little about who you are and where you’re from :nerd_face:
New

Any thoughts on Svelte?
Svelte is a radical new approach to building user interfaces. Whereas traditional frameworks like React and Vue...
New

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...
New
New

This looks like a stunning keycap set :orange_heart:
A LEGENDARY KEYBOARD LIVES ON
When you bought an Apple Macintosh computer in the e...
New

The V Programming Language
Simple language for building maintainable programs
V is already mentioned couple of times in the forum, but I...
New

Was just curious to see if any were around, found this one:
I got 51/100:
Not sure if it was meant to buy I am sure at times the b...
New

Author Spotlight
Rebecca Skinner
@RebeccaSkinner
Welcome to our latest author spotlight, where we sit down with Rebecca Skinner, auth...
New

Author Spotlight:
Peter Ullrich
@PJUllrich
Data is at the core of every business, but it is useless if nobody can access and analyze ...
New

Author Spotlight:
Sophie DeBenedetto
@SophieDeBenedetto
The days of the traditional request-response web application are long gone, b...
New
Categories:
Sub Categories:
Popular Portals
- /elixir
- /rust
- /ruby
- /wasm
- /erlang
- /phoenix
- /keyboards
- /rails
- /js
- /python
- /security
- /go
- /swift
- /vim
- /clojure
- /emacs
- /haskell
- /java
- /onivim
- /svelte
- /typescript
- /crystal
- /kotlin
- /c-plus-plus
- /tailwind
- /gleam
- /ocaml
- /react
- /elm
- /flutter
- /vscode
- /ash
- /opensuse
- /centos
- /php
- /deepseek
- /html
- /zig
- /scala
- /textmate
- /sublime-text
- /lisp
- /nixos
- /debian
- /react-native
- /agda
- /kubuntu
- /arch-linux
- /django
- /ubuntu
- /revery
- /manjaro
- /spring
- /nodejs
- /diversity
- /lua
- /slackware
- /c
- /julia
- /neovim