The match operator in Elixir

Three matches: destructuring a tuple, splitting a list, and pinning a bound value.

# = is a match, not an assignment: the shape on the left must fit the
# data on the right, and any bare names in it get bound.
{lat, lon} = {44.8, -68.7}
IO.puts("buoy anchored at #{lat}, #{lon}")

[flagship | escorts] = ["Puffin", "Skua", "Tern"]
IO.puts("#{flagship} leads; #{Enum.join(escorts, " and ")} follow")

# The pin operator ^ matches against a bound value instead of rebinding.
tide = "ebb"
{^tide, knots} = {"ebb", 2.5}
IO.puts("#{tide} current at #{knots} knots")

How it works

1. {lat, lon} = {44.8, -68.7} fits the shape on the left and binds both names.
2. [flagship | escorts] splits the fleet into its head and the list of the rest.
3. ^tide pins the existing binding, so the match asserts the value instead of rebinding it.

Keywords and builtins used here

• Enum
• IO

The run, in numbers

Lines

12

Characters to type

477

Tokens

107

Three-star pace

75 tpm

At the three-star pace of 75 tokens a minute, this run takes about 86 seconds.

Type this snippet

Step 1 of 3 in Pattern matching, step 4 of 27 in Language basics.

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