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erlangelixir

Variable assignment in Elixir

I have a question about variable assignment in Elixir. In Erlang, this would raise a no match of right hand side value:

X = 4.
X = 2.

However, it seems perfectly fine in Elixir to assign a value to a variable more than once. I am confused how pattern matching works in Elixir. How does Elixir differentiate between pattern matching and variable assignment? From what I understand, in Erlang, X is an unbound variable so it can be matched with anything, right? But once it is bound, pattern matching only works if it is the same value as X. So does Elixir not share the same concept of unbound variables as Erlang?

Solution

  • Yes, Elixir doesn't follow the same concept as Erlang in this regard. Elixir tries to be more accessible for developers less familiar with functional programming, especially Ruby developers. According to Pattern matching documentation you have to pin variable:

    iex(1)> x=4
4
iex(2)> ^x=2
** (MatchError) no match of right hand side value: 2

    Also, note that variables have to start with a lower case in Elixir.