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

iPaul
page 37 ANTLRInputStream input = new ANTLRInputStream(is); as of ANTLR 4 .8 should be: CharStream stream = CharStreams.fromStream(i...
New
simonpeter
When I try the command to create a pair of migration files I get an error. user=> (create-migration "guestbook") Execution error (Ill...
New
mikecargal
Title: Hands-On Rust (Chapter 11: prefab) Just played a couple of amulet-less games. With a bit of debugging, I believe that your can_p...
New
patoncrispy
I’m new to Rust and am using this book to learn more as well as to feed my interest in game dev. I’ve just finished the flappy dragon exa...
New
AndyDavis3416
@noelrappin Running the webpack dev server, I receive the following warning: ERROR in tsconfig.json TS18003: No inputs were found in c...
New
jskubick
I’m under the impression that when the reader gets to page 136 (“View Data with the Database Inspector”), the code SHOULD be able to buil...
New
digitalbias
Title: Build a Weather Station with Elixir and Nerves: Problem connecting to Postgres with Grafana on (page 64) If you follow the defau...
New
Henrai
Hi, I’m working on the Chapter 8 of the book. After I add add the point_offset, I’m still able to see acne: In the image above, I re...
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
redconfetti
Docker-Machine became part of the Docker Toolbox, which was deprecated in 2020, long after Docker Desktop supported Docker Engine nativel...
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
Exadra37
Oh just spent so much time on this to discover now that RancherOS is in end of life but Rancher is refusing to mark the Github repo as su...
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
PragmaticBookshelf
Build efficient applications that exploit the unique benefits of a pure functional language, learning from an engineer who uses Haskell t...
New
PragmaticBookshelf
Author Spotlight Rebecca Skinner @RebeccaSkinner Welcome to our latest author spotlight, where we sit down with Rebecca Skinner, auth...
New
AstonJ
If you want a quick and easy way to block any website on your Mac using Little Snitch simply… File > New Rule: And select Deny, O...
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
First poster: bot
zig/http.zig at 7cf2cbb33ef34c1d211135f56d30fe23b6cacd42 · ziglang/zig. General-purpose programming language and toolchain for maintaini...
New
mindriot
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

Sub Categories: