Effective Haskell (Pragmatic Bookshelf)
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‘PolyKinds GHC2021’ (page xx, line 12) is a duplicate entry. See last line on page xix.
(Book version P1.0)
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the (<>) operator would get passed to the function show instead of
the string we get back when we say show 1.
I think it should ...
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@RebeccaSkinner
On page 198, when phantom types are introduced, when listing other changes to the code example at hand, also this necess...
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@RebeccaSkinner
Both module statements in the code examples on pp. xvii and xviii in the Introduction (“Following Along with Example Cod...
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@RebeccaSkinner
The book seems to be missing an import statement like
λ import HaskellBook.Examples.Introduction.CreatingModules (Name ...
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Most Active Last Three Years

@RebeccaSkinner
Thanks you for this beautiful book.
Chapter 8 - p.317 3rd paragraph from the bottom
If you build your application and ...
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In toCsv (ePub p 157, dropLeadingComma will leave a leading space. In the case statement, the first case is ‘,’:s’ → s’ and it should be ...
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“You’ll notice that in all of the examples so far, we’ve created lists that only contain numbers” - this is incorrect, one of the first e...
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@RebeccaSkinner
In Effective Haskell Chapter 11 (~ p 410 in ePub), when creating the Encode and Decode instances for String, pack and un...
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Defining Functor for Either Section (p. 270 ff ePub):
The discussion of the kind error seems as thought kinds have not been introduced ...
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@RebeccaSkinner
In beta 9.0
A small typo near the bottom of p83:
“but it there are some extra moving parts”
Probably"it" should be dr...
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The function I am testing is handleNums on page 68.
It returns this error message:
λ: :reload
[1 of 1] Compiling Main ...
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Effective Haskell:Chapter 13 (B9 - PDF version) - infinite loop when running the ClassyArchiver code
Refer to pages 508-511
I get an infinite loop when running the original parseArchive function, after adding a variable called "archiveD...
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There’s a small typo in ch2 (B9.0), half way through the section Destructuring Values With Pattern Matching in the sentence:
As an exam...
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(I may be overthinking corner cases for a little example program)
If you pass in a list of guests with a duplicated food, like [(“Alice”...
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In ch3, section on Reading Type Errors, the error message presented for "one " :: Int with IsString seems non-standard, ie not from a min...
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Just noticed a typo in chapter 2, on the bottom of p55 of B9.0 it says:
pseduo-Haskell
I missed this on my first reading of the chapter...
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On p66 of B9.0 chapter 2:
combineLists as bs =
let a = head as
b = head bs
as' = tail as
bs' = tail bs
in if null...
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The text says "Just like function application at the value level, types for Haskell functions are also left-to-right associative, so inst...
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All the people learning programming, itself,
their 1st time,
would benefit, significantly,
from learning Git.
And the beginners won’t...
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Most Active Over Three Years

Title: Effective Haskell - Example doesn’t work (page 8)
Middle of page 8 says: "Create a new Main.hs and copy the example below to get ...
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“Much of this {difficult~>difficulty} is due to the complexity inherent in modern systems. ”
“Today, software needs to do more things...
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At the beginning of the Composing Functions subsection in Chapter 1 it says: “You’ve already done this kind of implicit function composit...
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Functions that accept arguments in any order are called “commutative”, not “associative”. Note that this is mentioned twice in the same p...
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At the end of “Depending on Other Files” (ePub p 153), it says “In the next section you’ll learn the basics of Haskell’s syntax and gramm...
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To be more concise and minimize the number of threads, I grouped the suggested corrections into one post.
A few notes on how I structure...
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In Chapter 8, (Viewing Text One Page at a Time), when defining groupsOf, it says we should use a polymorphic type in the type signature, ...
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The addPeano function switches the arguments in the recursive call. The implementation should be:
addPeano Z b = b
addPeano (S a) b = a...
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To be more concise and minimize the number of threads, I grouped the suggested corrections into one post.
A few notes on how I structure...
New

In the “Functions as Data Types” section of Chapter 4 (ePub p 113), the takeDigits parser is introduced as “we could take some digits fro...
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In the “Filtering List Elements” section, the party budget function is first called “foodBudget” and all subsequent reference are “partyB...
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On page 19, the last line of the guard clause code snippet:
| otherwise = “that’s an unfathomalbly big number”
has “unfathomably” missp...
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Title: Effective Haskell - lambda example would help (pages 8-9)
At the bottom of page 8 and the top of page 9 lambdas are described. I ...
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Effective Haskell Chapter 8
getTerminalSize (Epub p 243) used pure in the case statement and return in the definition of tputScreenDime...
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In the error handling section in Chapter 8:
In the first refactor (ePub p 202), it says “we’ll start by adding a second helper function...
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