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
Hello Brian,
I have some problems with running the code in your book. I like the style of the book very much and I have learnt a lot as...
New
Title: Web Development with Clojure, Third Edition - migrations/create not working: p159
When I execute the command:
user=> (create-...
New
Hello! On page xix of the preface, it says there is a community forum "… for help if your’re stuck on one of the exercises in this book… ...
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
When I run the coverage example to report on missing lines, I get:
pytest --cov=cards --report=term-missing ch7
ERROR: usage: pytest [op...
New
When running tox for the first time, I got the following error:
ERROR: InterpreterNotFound: python3.10
I realised that I was running ...
New
The allprojects block listed on page 245 produces the following error when syncing gradle:
“org.gradle.api.GradleScriptException: A prob...
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
@parrt
In the context of Chapter 4.3, the grammar Java.g4, meant to parse Java 6 compilation units, no longer passes ANTLR (currently 4....
New
root_layout: {PentoWeb.LayoutView, :root},
This results in the following following error:
no “root” html template defined for PentoWeb...
New
Other popular topics
Machine learning can be intimidating, with its reliance on math and algorithms that most programmers don't encounter in their regular wor...
New
Ruby, Io, Prolog, Scala, Erlang, Clojure, Haskell. With Seven Languages in Seven Weeks, by Bruce A. Tate, you’ll go beyond the syntax—and...
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
We have a thread about the keyboards we have, but what about nice keyboards we come across that we want? If you have seen any that look n...
New
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 ...
New
I ended up cancelling my Moonlander order as I think it’s just going to be a bit too bulky for me.
I think the Planck and the Preonic (o...
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
Small essay with thoughts on macOS vs. Linux:
I know @Exadra37 is just waiting around the corner to scream at me “I TOLD YOU SO!!!” but I...
New
Hello everyone! This thread is to tell you about what authors from The Pragmatic Bookshelf are writing on Medium.
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
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
- /flutter
- /elm
- /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
- /lua
- /diversity
- /julia
- /markdown
- /quarkus









