is there any way to define overload functions with different arity, e.g in C# I can just do:
foo(bar)
or
foo(bar, baz)
In Elixir, the only way to do that would be to put them in separate modules, which will get messy pretty quickly. Is there any way around it?
Edit: I had made a wrong assumption. The examples of overloaded functions I saw happened to have the same arity, so I (wrongly) assumed that this was a requirement. Functions are uniquely identified by their name and arity, so you can in fact overload functions with different arity.
In Erlang and Elixir, and unlike many other languages (such as C#), functions are uniquely identified by their name and arity, so technically foo(bar)
and foo(bar, baz)
are totally different functions. But that's really just a technicality, to write an 'overloaded' function in Elixir, you would write something like the following definition of sum
:
defmodule Math do
def sum(list), do: sum(list, 0)
def sum([], acc), do: acc
def sum([h|t], acc), do: sum(t, acc + h)
end
On this page see especially section 8.3 and following. Specifically this:
Function declarations also support guards and multiple clauses. If a function has several clauses, Elixir will try each clause until it finds one that matches. Here is an implementation of a function that checks if the given number is zero or not:
defmodule Math do
def zero?(0) do
true
end
def zero?(x) when is_number(x) do
false
end
end
Math.zero?(0) #=> true
Math.zero?(1) #=> false
Math.zero?([1,2,3])
#=> ** (FunctionClauseError)
Same function name with multiple overloads (although the concept is called clauses
in the documentation) in a single module.
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