PragProg Customers

Effective Haskell: Chapter 6 - HKT and Polymorphism

pennychase

pennychase

Effective Haskell: Chapter 6 - HKT and Polymorphism

In toCsv (ePub p 157, dropLeadingComma will leave a leading space. In the case statement, the first case is ‘,’:s’ → s’ and it should be ‘,’:’ ‘:s’ → s’

Also p 157. “Notice in the type signatures for the fold functions that we have a type class constraint on t, but in our type signature we’re applying the type a to t. That’s because t is a higher kinded type variable …” This is a bit terse (after reading it over a few times, I realized that this is really mind-blowing :slight_smile: ). I wonder if there could be some additional discussion relating the applying types (e.g., applying types to Either) to higher kinded variables.

3 comments
#errata/book-effective-haskell
2 764 3

Most Liked

pennychase

pennychase

The “Deriving Nullable” portion of the exercises could be expanded a bit. I’m not sure what is meant by being asked to “create derived instance of Nullable for optional types, while allowing you to easily select which distance you would like to use.”

1
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
2 764 3
Last post

Popular Pragmatic Bookshelf topics Top

abtin
PragProg Customers

Distributed Services With Go - gogoproto on linux
page 20: … protoc command… I had to additionally run the following go get commands in order to be able to compile protobuf code using go...
#errata/book-distributed-services-with-go
14 2953 7
New
brianokken
PragProg Customers

Python Testing with pytest: pytest now requires markers to be declared (downloadable code)
Many tasks_proj/tests directories exist in chapters 2, 3, 5 that have tests that use the custom markers smoke and get, which are not decl...
#errata/book-python-testing-with-pytest
2 1383 2
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
yulkin
PragProg Customers

Programming Flutter: Image.toByteData() does not exist (page40)
your book suggests to use Image.toByteData() to convert image to bytes, however I get the following error: "the getter ‘toByteData’ isn’t...
/book-programming-flutter#question
1 4102 2
New
mikecargal
PragProg Customers

Hands-on Rust: question about get_component
Title: Hands-on Rust: question about get_component (page 295) (feel free to respond. “You dug you’re own hole… good luck”) I have somet...
#question/book-hands-on-rust
1 1167 5
New
alanq
PragProg Customers

Modern Front-End Development for Rails: Can't get TURBO_STREAM format in some cases
This isn’t directly about the book contents so maybe not the right forum…but in some of the code apps (e.g. turbo/06) it sends a TURBO_ST...
#question/book-modern-front-end-development-for-rails
1 1386 7
New
jskubick
PragProg Customers

Kotlin and Android Development featuring Jetpack: SwitchCompat's thumbTint and trackTint being ignored (page 76)
I think I might have found a problem involving SwitchCompat, thumbTint, and trackTint. As entered, the SwitchCompat changes color to hol...
#errata/book-kotlin-and-android-development-featuring-jetpack
0 2749 2
New
jskubick
PragProg Customers

Kotlin and Android Development featuring Jetpack: Error in generated Game.java (page 136)
I’m under the impression that when the reader gets to page 136 (“View Data with the Database Inspector”), the code SHOULD be able to buil...
#question/book-kotlin-and-android-development-featuring-jetpack
2 1172 8
New
adamwoolhether
PragProg Customers

Distributed Services With Go: Unable to pass readiness/liveness checks. (page 210, 215)
I’m not quite sure what’s going on here, but I’m unable to have to containers successfully complete the Readiness/Liveness checks. I’m im...
/book-distributed-services-with-go
5 1420 5
New
ggerico
PragProg Customers

Programming Machine Learning: some plot files are throwing error
I got this error when executing the plot files on macOS Ventura 13.0.1 with Python 3.10.8 and matplotlib 3.6.1: programming_ML/code/03_...
#question/book-programming-machine-learning
1 3055 5
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
1063 24245 395
New
PragmaticBookshelf
Backend>Learning Resources

Seven Languages in Seven Weeks
Ruby, Io, Prolog, Scala, Erlang, Clojure, Haskell. With Seven Languages in Seven Weeks, by Bruce A. Tate, you’ll go beyond the syntax—and...
pragprog.com
#pragprog/clojure/erlang/haskell/prolog/ruby/scala#published-book/book-seven-languages-in-seven-weeks
5 5730 1
New
PragmaticBookshelf
Android>Learning Resources

Kotlin and Android Development featuring Jetpack: Build Better, Safer Android Apps
Start building native Android apps the modern way in Kotlin with Jetpack's expansive set of tools, libraries, and best practices. Learn h...
pragprog.com
#pragprog#android#game-dev/kotlin#published-book/book-kotlin-and-android-development-featuring-jetpack
7 5084 1
New
AstonJ
Backend>Questions

Erlang's not installing on macOS Big Sur "You are natively building Erlang/OTP for a later version of MacOSX than current version"
Just done a fresh install of macOS Big Sur and on installing Erlang I am getting: asdf install erlang 23.1.2 Configure failed. checking ...
#macos/erlang#big-sur#asdf
10 6212 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
84 14528 26
New
PragmaticBookshelf
Backend>Learning Resources

Python Testing with pytest, Second Edition
Create efficient, elegant software tests in pytest, Python's most powerful testing framework. Brian Okken @brianokken Edited by Kat...
pragprog.com
#pragprog/python#published-book/book-python-testing-with-pytest-second-edition
16 7461 4
New
AstonJ
Science/Tech>Health & Diet

David Sinclair's new Lifespan podcast
We’ve talked about his book briefly here but it is quickly becoming obsolete - so he’s decided to create a series of 7 podcasts, the firs...
#health#podcasts#bio-hackers#david-sinclair
87 6790 49
New
First poster: bot
General Dev>In The News

Zig now has built-in HTTP server and client in std
zig/http.zig at 7cf2cbb33ef34c1d211135f56d30fe23b6cacd42 · ziglang/zig. General-purpose programming language and toolchain for maintaini...
github.com
/zig#http
0 5624 0
New
PragmaticBookshelf
Backend>Learning Resources

Kotlin Coroutine Confidence
Escape callback hell and ship fast, clean code that reads as smoothly as it runs. Squash bugs and stamp out memory leaks with an intuitiv...
pragprog.com
#pragprog/java/kotlin#published-book/book-kotlin-coroutine-confidence
14 3688 10
New
PragmaticBookshelf
Backend>Learning Resources

Programming Clojure, Fourth Edition
Quickly turn complex problems into simple, working solutions using functional programming, safe concurrency, and the expressive tools of ...
pragprog.com
#pragprog
4 1975 3
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!"

Linux New Media

Publishing Linux Magazine, ADMIN, and MakerSpace for 25+ years.

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!"

Linux New Media

Publishing Linux Magazine, ADMIN, and MakerSpace for 25+ years.

View all our sponsors ❯

We're in Beta

About us Mission Statement See our Roadmap