Advanced Functional Programming with Elixir: Problem Running Code Example

Pragmatic Bookshelf PragProg Customers
,
1

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!