imeraj

imeraj

Advanced Functional Programming with Elixir: Problem Running Code Example

I am reading this book with great enthusiasm.

So far the code works great but while running the examples in Predicates That Span Contexts section I am encountering some function arity errors as below -

iex(13)> FunPark.Ride.eligible?(alice, tea_cup)
** (FunctionClauseError) no function clause matching in FunPark.Monoid.FunPark.Monoid.PredAll.wrap/2

    The following arguments were given to FunPark.Monoid.FunPark.Monoid.PredAll.wrap/2:

        # 1
        %FunPark.Monoid.PredAll{
          value: &FunPark.Monoid.PredAll.default_pred?/1
        }

        # 2
        #Function<1.2796843/2 in FunPark.Ride.tall_enough?>

    Attempted function clauses (showing 1 out of 1):

        def wrap(%FunPark.Monoid.PredAll{}, value) when is_function(value, 1)

Apparently, we are passing two arguments instead of one here -

def eligible?(%Patron{} = patron, %__MODULE__{} = ride),
    do: p_all([&tall_enough?/2, &old_enough?/2]).(patron, ride)

I ran the book’s sample code and it works fine. But it has code with curry.

I am wondering if the example code from this section is supposed to run without curry as I am typing in the code as I go.

Thanks!

First Post!

luistavera

luistavera

Hi

I am running into the same issue. I think this is an error in the book since the Predicate expects a function with arity 1. The following works:
def elegible?(%Patron{} = patron, %MODULE{} = ride) do
te = fn patron → tall_enough?(patron, ride) end
oe = fn patron → old_enough?(patron, ride) end
p_all([te, oe]).(patron)
end
Cheers

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
yulkin
your book suggests to use Image.toByteData() to convert image to bytes, however I get the following error: "the getter ‘toByteData’ isn’t...
New
herminiotorres
Hi @Margaret , On page VII the book tells us the example and snippets will be all using Elixir version 1.11 But on page 3 almost the en...
New
New
jskubick
I’m running Android Studio “Arctic Fox” 2020.3.1 Patch 2, and I’m embarrassed to admit that I only made it to page 8 before running into ...
New
oaklandgit
Hi, I completed chapter 6 but am getting the following error when running: thread 'main' panicked at 'Failed to load texture: IoError(O...
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
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
dtonhofer
@parrt In the context of Chapter 4.3, the grammar Java.g4, meant to parse Java 6 compilation units, no longer passes ANTLR (currently 4....
New
New

Other popular topics Top

PragmaticBookshelf
Learn from the award-winning programming series that inspired the Elixir language, and go on a step-by-step journey through the most impo...
New
New
AstonJ
I ended up cancelling my Moonlander order as I think it’s just going to be a bit too bulky for me. I think the Planck and the Preonic (o...
New
husaindevelop
Inside our android webview app, we are trying to paste the copied content from another app eg (notes) using navigator.clipboard.readtext ...
New
PragmaticBookshelf
25 puzzles that will make you a better C programmer by challenging your knowledge of the language, and explaining the technical details o...
New
PragmaticBookshelf
Get the comprehensive, insider information you need for Rails 8 with the new edition of this award-winning classic. Sam Ruby @rubys ...
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
PragmaticBookshelf
Escape callback hell and ship fast, clean code that reads as smoothly as it runs. Squash bugs and stamp out memory leaks with an intuitiv...
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
PragmaticBookshelf
Use advanced functional programming principles, practical Domain-Driven Design techniques, and production-ready Elixir code to build scal...
New

Sub Categories: