molleweide

molleweide

Effective Haskell: ch 2 > destructuring lists

  1. The function I am testing is handleNums on 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.
  1. I sort of understand the err msg but I add this info here so you can see that this can happen to a reader.

  2. Did I post this information under the correct category. Is “errata” correct or should I have chose something else?

  3. The book is great! I’m chugging along and it feels really good.

First Post!

RebeccaSkinner

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.

Where Next?

Popular Pragmatic Bookshelf topics Top

jesse050717
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
jamis
The following is cross-posted from the original Ray Tracer Challenge forum, from a post by garfieldnate. I’m cross-posting it so that the...
New
herminiotorres
Hi! I know not the intentions behind this narrative when called, on page XI: mount() |> handle_event() |> render() but the correc...
New
HarryDeveloper
Hi @venkats, It has been mentioned in the description of ‘Supervisory Job’ title that 2 things as mentioned below result in the same eff...
New
Charles
In general, the book isn’t yet updated for Phoenix version 1.6. On page 18 of the book, the authors indicate that an auto generated of ro...
New
taguniversalmachine
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
s2k
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
jwandekoken
Book: Programming Phoenix LiveView, page 142 (157/378), file lib/pento_web/live/product_live/form_component.ex, in the function below: d...
New
andreheijstek
After running /bin/setup, the first error was: The foreman' command exists in these Ruby versions: That was easy to fix: gem install fore...
New
mcpierce
@mfazio23 I’ve applied the changes from Chapter 5 of the book and everything builds correctly and runs. But, when I try to start a game,...
New

Other popular topics Top

dasdom
No chair. I have a standing desk. This post was split into a dedicated thread from our thread about chairs :slight_smile:
New
AstonJ
Curious to know which languages and frameworks you’re all thinking about learning next :upside_down_face: Perhaps if there’s enough peop...
New
AstonJ
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
Margaret
Hello everyone! This thread is to tell you about what authors from The Pragmatic Bookshelf are writing on Medium.
1147 29994 760
New
PragmaticBookshelf
Author Spotlight Mike Riley @mriley This month, we turn the spotlight on Mike Riley, author of Portable Python Projects. Mike’s book ...
New
New
PragmaticBookshelf
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
New
CommunityNews
A Brief Review of the Minisforum V3 AMD Tablet. Update: I have created an awesome-minisforum-v3 GitHub repository to list information fo...
New
PragmaticBookshelf
A concise guide to MySQL 9 database administration, covering fundamental concepts, techniques, and best practices. Neil Smyth MySQL...
New

Sub Categories: