molleweide
Effective Haskell: ch 2 > destructuring lists
- The function I am testing is
handleNumson page 68.
It returns this error message:
λ: :reload
[1 of 1] Compiling Main ( Chapter2.hs, interpreted )
Chapter2.hs:306:1: error:
• Non type-variable argument
in the constraint: Show ((a -> Bool) -> Bool)
(Use FlexibleContexts to permit this)
• When checking the inferred type
handleNums :: forall a.
(Integral a, Show ((a -> Bool) -> Bool), Num ((a -> Bool) -> Bool),
Eq ((a -> Bool) -> Bool)) =>
[(a -> Bool) -> Bool] -> [Char]
|
306 | handleNums l =
| ^^^^^^^^^^^^^^...
Failed, no modules loaded.
-
I sort of understand the err msg but I add this info here so you can see that this can happen to a reader.
-
Did I post this information under the correct category. Is “errata” correct or should I have chose something else?
-
The book is great! I’m chugging along and it feels really good.
First Post!
RebeccaSkinner
Author of Effective Haskell
Hi! Can you share the code that you are trying to load. I can’t reproduce this error from the example locally.
Popular Pragmatic Bookshelf topics
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...
New
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...
New
Page 28: It implements io.ReaderAt on the store type.
Sorry if it’s a dumb question but was the io.ReaderAt supposed to be io.ReadAt?
...
New
Hi! I know not the intentions behind this narrative when called, on page XI:
mount() |> handle_event() |> render()
but the correc...
New
I ran this command after installing the sample application:
$ cards add do something --owner Brian
And got a file not found error:
Fil...
New
Hi,
I am getting an error I cannot figure out on my test.
I have what I think is the exact code from the book, other than I changed “us...
New
Hi all,
currently I wonder how the Tailwind colours work (or don’t work).
For example, in app/views/layouts/application.html.erb I have...
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
Hello faithful readers! If you have tried to follow along in the book, you are asked to start up the dev environment via dx/build and ar...
New
@mfazio23
Android Studio will not accept anything I do when trying to use the Transformations class, as described on pp. 140-141. Googl...
New
Other popular topics
Algorithms and data structures are much more than abstract concepts. Mastering them enables you to write code that runs faster and more e...
New
I know that -t flag is used along with -i flag for getting an interactive shell. But I cannot digest what the man page for docker run com...
New
Thanks to @foxtrottwist’s and @Tomas’s posts in this thread: Poll: Which code editor do you use? I bought Onivim! :nerd_face:
https://on...
New
In case anyone else is wondering why Ruby 3 doesn’t show when you do asdf list-all ruby :man_facepalming: do this first:
asdf plugin-upd...
New
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...
New
Author Spotlight:
VM Brasseur
@vmbrasseur
We have a treat for you today! We turn the spotlight onto Open Source as we sit down with V...
New
Develop, deploy, and debug BEAM applications using BEAMOps: a new paradigm that focuses on scalability, fault tolerance, and owning each ...
New
A concise guide to MySQL 9 database administration, covering fundamental concepts, techniques, and best practices.
Neil Smyth
MySQL...
New
Ok, well here are some thoughts and opinions on some of the ergonomic keyboards I have, I guess like mini review of each that I use enoug...
New
Use advanced functional programming principles, practical Domain-Driven Design techniques, and production-ready Elixir code to build scal...
New
Categories:
Sub Categories:
Popular Portals
- /elixir
- /rust
- /wasm
- /ruby
- /erlang
- /phoenix
- /keyboards
- /python
- /js
- /rails
- /security
- /go
- /swift
- /vim
- /clojure
- /java
- /emacs
- /haskell
- /svelte
- /onivim
- /typescript
- /kotlin
- /c-plus-plus
- /crystal
- /tailwind
- /react
- /gleam
- /ocaml
- /elm
- /flutter
- /ash
- /vscode
- /html
- /opensuse
- /zig
- /centos
- /deepseek
- /php
- /scala
- /react-native
- /lisp
- /sublime-text
- /textmate
- /nixos
- /debian
- /agda
- /deno
- /django
- /kubuntu
- /arch-linux
- /nodejs
- /spring
- /ubuntu
- /revery
- /manjaro
- /julia
- /lua
- /diversity
- /markdown
- /quarkus









