juhp

juhp

Effective Haskell: "one" :: Int error message (p99)

In ch3, section on Reading Type Errors, the error message presented for "one " :: Int with IsString seems non-standard, ie not from a minimal ghci session perhaps? Also note the space after e.

For all current GHC 9 versions I get;

ghci> "one" :: Int

<interactive>:1:1: error:
    • Couldn't match type ‘[Char]’ with ‘Int’
      Expected: Int
        Actual: String
    • In the expression: "one" :: Int
      In an equation for ‘it’: it = "one" :: Int

(ghc-8.10 is slightly different but also no IsString.)

Of course it’s quite likely one will run into the IsString error IRL… :slight_smile:

Most Liked

RebeccaSkinner

RebeccaSkinner

Author of Effective Haskell

Oh yeah, that’s a great catch. I had a few default extensions enabled in ghci, including OverloadedStrings. I’ll get some errata up soon with the set of default extensions and some additional explanation. Thanks!

Where Next?

Popular Pragmatic Bookshelf topics Top

johnp
Running the examples in chapter 5 c under pytest 5.4.1 causes an AttributeError: ‘module’ object has no attribute ‘config’. In particula...
New
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
herminiotorres
Hi! I know not the intentions behind this narrative when called, on page XI: mount() |&gt; handle_event() |&gt; render() but the correc...
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
rmurray10127
Title: Intuitive Python: docker run… denied error (page 2) Attempted to run the docker command in both CLI and Powershell PS C:\Users\r...
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
curtosis
Running mix deps.get in the sensor_hub directory fails with the following error: ** (Mix) No SSH public keys found in ~/.ssh. An ssh aut...
New
mert
AWDWR 7, page 152, page 153: Hello everyone, I’m a little bit lost on the hotwire part. I didn’t fully understand it. On page 152 @rub...
New
tkhobbes
After some hassle, I was able to finally run bin/setup, now I have started the rails server but I get this error message right when I vis...
New
a.zampa
@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

Other popular topics Top

Devtalk
Hello Devtalk World! Please let us know a little about who you are and where you’re from :nerd_face:
New
malloryerik
Any thoughts on Svelte? Svelte is a radical new approach to building user interfaces. Whereas traditional frameworks like React and Vue...
New
Exadra37
Please tell us what is your preferred monitor setup for programming(not gaming) and why you have chosen it. Does your monitor have eye p...
New
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
DevotionGeo
The V Programming Language Simple language for building maintainable programs V is already mentioned couple of times in the forum, but I...
New
AstonJ
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
PragmaticBookshelf
Author Spotlight Rebecca Skinner @RebeccaSkinner Welcome to our latest author spotlight, where we sit down with Rebecca Skinner, auth...
New
PragmaticBookshelf
Author Spotlight: Peter Ullrich @PJUllrich Data is at the core of every business, but it is useless if nobody can access and analyze ...
New
PragmaticBookshelf
Author Spotlight: Sophie DeBenedetto @SophieDeBenedetto The days of the traditional request-response web application are long gone, b...
New

Sub Categories: