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

iPaul
page 37 ANTLRInputStream input = new ANTLRInputStream(is); as of ANTLR 4 .8 should be: CharStream stream = CharStreams.fromStream(i...
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
mikecargal
Title: Hands-on Rust: question about get_component (page 295) (feel free to respond. “You dug you’re own hole… good luck”) I have somet...
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
hazardco
On page 78 the following code appears: &lt;%= 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
Keton
When running the program in chapter 8, “Implementing Combat”, the printout Health before attack was never printed so I assumed something ...
New
redconfetti
Docker-Machine became part of the Docker Toolbox, which was deprecated in 2020, long after Docker Desktop supported Docker Engine nativel...
New
dachristenson
I just bought this book to learn about Android development, and I’m already running into a major issue in Ch. 1, p. 20: “Update activity...
New
New

Other popular topics Top

AstonJ
If it’s a mechanical keyboard, which switches do you have? Would you recommend it? Why? What will your next keyboard be? Pics always w...
New
PragmaticBookshelf
Write Elixir tests that you can be proud of. Dive into Elixir’s test philosophy and gain mastery over the terminology and concepts that u...
New
AstonJ
Or looking forward to? :nerd_face:
503 15149 280
New
dasdom
No chair. I have a standing desk. This post was split into a dedicated thread from our thread about chairs :slight_smile:
New
AstonJ
Just done a fresh install of macOS Big Sur and on installing Erlang I am getting: asdf install erlang 23.1.2 Configure failed. checking ...
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
Help
I am trying to crate a game for the Nintendo switch, I wanted to use Java as I am comfortable with that programming language. Can you use...
New
PragmaticBookshelf
Author Spotlight Rebecca Skinner @RebeccaSkinner Welcome to our latest author spotlight, where we sit down with Rebecca Skinner, auth...
New
PragmaticBookshelf
Build modern server-driven web applications using htmx. Whatever programming language you use, you’ll write less (and cleaner) code. ...
New
AstonJ
This is a very quick guide, you just need to: Download LM Studio: https://lmstudio.ai/ Click on search Type DeepSeek, then select the o...
New

Sub Categories: