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

New
telemachus
Python Testing With Pytest - Chapter 2, warnings for “unregistered custom marks” While running the smoke tests in Chapter 2, I get these...
New
sdmoralesma
Title: Web Development with Clojure, Third Edition - migrations/create not working: p159 When I execute the command: user=> (create-...
New
raul
Hi Travis! Thank you for the cool book! :slight_smile: I made a list of issues and thought I could post them chapter by chapter. I’m rev...
New
AleksandrKudashkin
On the page xv there is an instruction to run bin/setup from the main folder. I downloaded the source code today (12/03/21) and can’t see...
New
cro
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
jeremyhuiskamp
Title: Web Development with Clojure, Third Edition, vB17.0 (p9) The create table guestbook syntax suggested doesn’t seem to be accepted ...
New
brunogirin
When installing Cards as an editable package, I get the following error: ERROR: File “setup.py” not found. Directory cannot be installe...
New
hazardco
On page 78 the following code appears: <%= link_to ‘Destroy’, product, class: ‘hover:underline’, method: :delete, data: { confirm...
New
creminology
Skimming ahead, much of the following is explained in Chapter 3, but new readers (like me!) will hit a roadblock in Chapter 2 with their ...
New

Other popular topics Top

PragmaticBookshelf
Free and open source software is the default choice for the technologies that run our world, and it’s built and maintained by people like...
New
AstonJ
Or looking forward to? :nerd_face:
498 13326 269
New
AstonJ
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
dimitarvp
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
DevotionGeo
The V Programming Language Simple language for building maintainable programs V is already mentioned couple of times in the forum, but I...
New
New
DevotionGeo
I have always used antique keyboards like Cherry MX 1800 or Cherry MX 8100 and almost always have modified the switches in some way, like...
New
NewsBot
Node.js v22.14.0 has been released. Link: Release 2025-02-11, Version 22.14.0 'Jod' (LTS), @aduh95 · nodejs/node · GitHub
New
RobertRichards
Hair Salon Games for Girls Fun Girls Hair Saloon game is mainly developed for kids. This game allows users to select virtual avatars to ...
New
PragmaticBookshelf
Fight complexity and reclaim the original spirit of agility by learning to simplify how you develop software. The result: a more humane a...
New

Sub Categories: