A Beginner’s Guide to Erlang: Functions and Data Types

Now that you’ve run your first Erlang program, it’s time to dive deeper into its core components: Erlang functions and its unique data types. As a functional language, everything in Erlang revolves around functions. Understanding how they work, along with the immutable data structures they operate on, is key to mastering the language and its concurrent capabilities.

💻 Core Erlang Data Types

Erlang has several fundamental data types. A key concept is immutability, meaning once a variable is assigned, its value cannot be changed.

• Numbers: Erlang supports integers (e.g., 123) and floats (e.g., 0.987).
• Atoms: These are constants where the value is the name itself, like linux or ok. They are used to represent distinct, non-numeric values.
• Tuples: A fixed-size, compound data type for grouping a number of items, enclosed in curly braces: {linux, 1}.
• Lists: A variable-size, compound data type, enclosed in square brackets: [a, b, 3, {a, b}]. Strings in Erlang are simply lists of characters.
• Maps: A key-value data structure, perfect for storing associative data: #{country => greece, city => athens}.

💻 Working with Functions

Functions in Erlang are sequences of clauses separated by semicolons and ending with a period. A function’s identity is defined by its name and its arity (number of arguments), written as functionName/arity. Erlang also supports anonymous functions, also known as ‘funs’, which can be assigned to variables and passed as arguments to other functions.

F = fun(X) -> 2 * X end.
Five = fun(N, Function) -> 5 * Function(N) end.

Five(10, F).

In this example:

• F is an anonymous function that doubles its input.
• Five is an anonymous function that takes a number N and another function Function as arguments.
• Five(10, F) calls Five, which in turn calls F(10) and multiplies the result by 5, yielding 100.

Erlang also relies heavily on pattern matching and guards within function clauses to control program flow, which is often used in place of traditional if/else statements.

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