Let's dive right in.

Rethink Assignment

In programming, you typically assign a variable with an = sign. In math, = means something else entirely. It means the two terms on either side of the sign are equivalent. That's the way it is with Elixir.

When Elixir sees an = it will try to make both sides equivalent. When you call a function, Elixir will do the same thing with the arguments you pass: pattern matching against the function's argument list.

You've already seen a little of this in the previous chapters. Let's take a look at a few more examples (feel free to open up iex and type these examples in):

#a simple assignment
pattern = "match"

"pat" <> tern = "pattern match"
#a little weirder, the variable 'tern' = "tern match"

[1, x, 5] = [1, 10, 5]
#something straightforward: x = 10

This is, in a sense, destructuring assignment that you would see in JavaScript, Ruby, ES6:

var [x, y, z] = [1,2,3];

But Pattern Matching is a whole lot more than this. While you can indeed use it to assign values, it's much more useful when used with function calls.