Let's say I have something like:
Enum.map(list, fn(x) -> String.duplicate("a", someValue * x) end)
But instead, I'd like to pass the String.duplicate/2 function as an argument in order to simplify my code:
Enum.map(list, &String.duplicate/2)
I know you can do it for arity 1 functions:
Enum.map(list, &String.downcase/1)
Thanks!
You can't pass a function to Enum.map
with an arity of 2 as Enum.map
calls your function with each element in the list as an argument. If you use another function like Enum.reduce
then it expects a function with an arity of 2.
This is an example of the String.downcase/1
function being called with each item in the list:
Enum.map(["FOO", "BAR", "BAZ"], fn(x) -> String.downcase(x) end)
# String.downcase("FOO")
# String.downcase("BAR")
# String.downcase("BAZ")
In your example with duplicate, you are trying to call String.duplicate/2
with a single argument (the string "FOO").
You can use the capture syntax to create a function (this is a shorthand way of defining the function you provided):
Enum.map([1,2,3], &String.duplicate("a", &1))
You can also define a named function in your module that only requires one argument, for example:
Enum.map([1, 2, 3], &duplicate_foo/1)
def duplicate_foo(times), do: String.duplicate("a", times)