Control Flow

As mentioned in the previous post on functions, control flow is where we first start to really feel the difference of thinking elixir vs a C-Style language. Elixir’s control flow can be broken into 5 concepts: if, with, case, cond, and as a more general concept, pattern matching.

If/else/unless

If statements are pretty much as you’d expect, with a few notable differences

let num = 2;
if (num === 2){
  console.log("2");
} else {
  console.log("Not 2");
}

num = 2
if num == 2 do
  IO.puts"2"
else
  IO.puts"Not 2"
end

If/do and else/end replace brackets for wrapping control.

Bonus: Ternary

One thing I (ab)used in TypeScript was the use of the ternary operator. Elixir has its own form.

let sheWalkedAwayFromMe = true;
let age = sheWalkedAwayFromMe ? 23 : 21;

she_walked_away_from_me = true
age = if she_walked_away_from_me, do: 23, else: 21

If statements, as well as all control flow statements can be used in assignments. For example, we could write the ternary from above in expanded form

she_walked_away_from_me = true
age = 
  if she_walked_away_from_me do 
    23
  else
    21
  end

and age would be 23. It was hard to wrap my head around that at first, but you’ll find it very useful in some situations.

with

With statements… what the hell are they even for really?

Pattern Matching

case

cond