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
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
page 37
ANTLRInputStream input = new ANTLRInputStream(is);
as of ANTLR 4 .8 should be:
CharStream stream = CharStreams.fromStream(i...
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
your book suggests to use Image.toByteData() to convert image to bytes, however I get the following error: "the getter ‘toByteData’ isn’t...
New
I am working on the “Your Turn” for chapter one and building out the restart button talked about on page 27. It recommends looking into ...
New
Hello! Thanks for the great book.
I was attempting the Trie (chap 17) exercises and for number 4 the solution provided for the autocorre...
New
I think I might have found a problem involving SwitchCompat, thumbTint, and trackTint.
As entered, the SwitchCompat changes color to hol...
New
Hi, I have just acquired Michael Fazio’s “Kotlin and Android Development” to learn about game programming for Android. I have a game in p...
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
root_layout: {PentoWeb.LayoutView, :root},
This results in the following following error:
no “root” html template defined for PentoWeb...
New
Other popular topics
If it’s a mechanical keyboard, which switches do you have?
Would you recommend it? Why?
What will your next keyboard be?
Pics always w...
New
SpaceVim seems to be gaining in features and popularity and I just wondered how it compares with SpaceMacs in 2020 - anyone have any thou...
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
You might be thinking we should just ask who’s not using VSCode :joy: however there are some new additions in the space that might give V...
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
If you are experiencing Rails console using 100% CPU on your dev machine, then updating your development and test gems might fix the issu...
New
Intensively researching Erlang books and additional resources on it, I have found that the topic of using Regular Expressions is either c...
New
Author Spotlight
Dmitry Zinoviev
@aqsaqal
Today we’re putting our spotlight on Dmitry Zinoviev, author of Data Science Essentials in ...
New
Author Spotlight
Jamis Buck
@jamis
This month, we have the pleasure of spotlighting author Jamis Buck, who has written Mazes for Prog...
New
New
Categories:
Sub Categories:
Popular Portals
- /elixir
- /rust
- /ruby
- /wasm
- /erlang
- /phoenix
- /keyboards
- /python
- /js
- /rails
- /security
- /go
- /swift
- /vim
- /clojure
- /emacs
- /haskell
- /java
- /svelte
- /onivim
- /typescript
- /kotlin
- /crystal
- /c-plus-plus
- /tailwind
- /react
- /gleam
- /ocaml
- /flutter
- /elm
- /vscode
- /ash
- /html
- /opensuse
- /centos
- /zig
- /deepseek
- /php
- /scala
- /react-native
- /sublime-text
- /lisp
- /textmate
- /debian
- /nixos
- /agda
- /kubuntu
- /django
- /arch-linux
- /deno
- /nodejs
- /ubuntu
- /revery
- /spring
- /manjaro
- /lua
- /diversity
- /julia
- /markdown
- /slackware








