Elixir Fundamentals & Pattern Matching

Elixir runs on BEAM — the Erlang VM built by Ericsson in the 1980s for telecom systems requiring 99.9999999% (nine-nines) uptime. BEAM runs millions of lightweight processes (not OS threads), each isolated with its own memory. A crashed process does not bring down others. This architecture makes Elixir naturally fault-tolerant and horizontally scalable — the same properties that attracted WhatsApp and Discord.

Basic Types and Immutability

Elixir types: integers, floats, booleans, atoms (:ok, :error, :hello), strings (UTF-8 binaries), lists [1,2,3], tuples {1,2,3}, maps %{key: value}, and nil. All data is immutable — rebinding a variable creates a new binding, it does not mutate the old value. Atoms are constants whose name is their value; :ok and :error are the most common return value conventions.

Pattern Matching

= in Elixir is the match operator, not assignment. '3 = 3' succeeds; '3 = 4' raises MatchError. '{:ok, value} = {:ok, 42}' binds value to 42. '[head | tail] = [1,2,3]' binds head=1, tail=[2,3]. Pattern matching in function clauses, case expressions, and receive blocks is the primary control flow mechanism. The _ wildcard matches anything without binding.

# Basic pattern matching
{:ok, value} = {:ok, 42}
IO.puts(value)  # 42

# Function with multiple clauses
defmodule Math do def factorial(0), do: 1 def factorial(n) when n > 0, do: n * factorial(n - 1) def fib(0), do: 0 def fib(1), do: 1 def fib(n), do: fib(n-1) + fib(n-2)
end

IO.puts Math.factorial(10)  # 3628800
IO.puts Math.fib(10) # 55

# Case expression
result = {:error, "not found"}
message = case result do {:ok, val}  -> "Success: #{val}" {:error, e} -> "Error: #{e}" _ -> "Unknown"
end
IO.puts message  # Error: not found

# Pipe operator
"  hello world  "
|> String.trim()
|> String.upcase()
|> String.split(" ")
|> Enum.join("-")
|> IO.puts()  # HELLO-WORLD