# Basic types In this chapter we will learn more about Elixir basic types: integers, floats, booleans, atoms, and strings. Other data types, such as lists and tuples, will be explored in the next chapter. ```elixir iex> 1 # integer iex> 0x1F # integer iex> 1.0 # float iex> true # boolean iex> :atom # atom / symbol iex> "elixir" # string iex> [1, 2, 3] # list iex> {1, 2, 3} # tuple ``` ## Basic arithmetic Open up `iex` and type the following expressions: ```elixir iex> 1 + 2 3 iex> 5 * 5 25 iex> 10 / 2 5.0 ``` Notice that `10 / 2` returned a float `5.0` instead of an integer `5`. This is expected. In Elixir, the operator [`/`](`//2`) always returns a float. If you want to do integer division or get the division remainder, you can invoke the [`div`](`div/2`) and [`rem`](`rem/2`) functions: ```elixir iex> div(10, 2) 5 iex> div 10, 2 5 iex> rem 10, 3 1 ``` Notice that Elixir allows you to drop the parentheses when invoking functions that expect one or more arguments. This feature gives a cleaner syntax when writing declarations and control-flow constructs. However, Elixir developers generally prefer to use parentheses. Elixir also supports shortcut notations for entering binary, octal, and hexadecimal numbers: ```elixir iex> 0b1010 10 iex> 0o777 511 iex> 0x1F 31 ``` Float numbers require a dot followed by at least one digit and also support `e` for scientific notation: ```elixir iex> 1.0 1.0 iex> 1.0e-10 1.0e-10 ``` Floats in Elixir are 64-bit precision. You can invoke the [`round`](`round/1`) function to get the closest integer to a given float, or the [`trunc`](`trunc/1`) function to get the integer part of a float. ```elixir iex> round(3.58) 4 iex> trunc(3.58) 3 ``` Finally, we work with different data types, we will learn Elixir provides several predicate functions to check for the type of a value. For example, [`is_integer`](`is_integer/1`) can be used to check if a value is an integer or not: ```elixir iex> is_integer(1) true iex> is_integer(2.0) false ``` You can also use [`is_float`](`is_float/1`) or [`is_number`](`is_number/1`) to check, respectively, if an argument is a float, or either an integer or float. ## Booleans and `nil` Elixir supports `true` and `false` as booleans: ```elixir iex> true true iex> true == false false ``` Elixir also provides three boolean operators: [`or`](`or/2`), [`and`](`and/2`), and [`not`](`not/1`). These operators are strict in the sense that they expect something that evaluates to a boolean (`true` or `false`) as their first argument: ```elixir iex> true and true true iex> false or is_boolean(true) true ``` Providing a non-boolean will raise an exception: ```elixir iex> 1 and true ** (BadBooleanError) expected a boolean on left-side of "and", got: 1 ``` `or` and `and` are short-circuit operators. They only execute the right side if the left side is not enough to determine the result: ```elixir iex> false and raise("This error will never be raised") false iex> true or raise("This error will never be raised") true ``` Elixir also provides the concept of `nil`, to indicate the absence of a value, and a set of logical operators that also manipulate `nil`: `||/2`, `&&/2`, and `!/1`. For these operators, `false` and `nil` are considered "falsy", all other values are considered "truthy": ```elixir # or iex> 1 || true 1 iex> false || 11 11 # and iex> nil && 13 nil iex> true && 17 17 # not iex> !true false iex> !1 false iex> !nil true ``` Similarly, values like `0` and `""`, which some other programming languages consider to be "falsy", are also "truthy" in Elixir. As a rule of thumb, use `and`, `or` and `not` when you are expecting booleans. If any of the arguments are non-boolean, use `&&`, `||` and `!`. ## Atoms An atom is a constant whose value is its own name. Some other languages call these symbols. They are often useful to enumerate over distinct values, such as: ```elixir iex> :apple :apple iex> :orange :orange iex> :watermelon :watermelon ``` Atoms are equal if their names are equal. ```elixir iex> :apple == :apple true iex> :apple == :orange false ``` Often they are used to express the state of an operation, by using values such as `:ok` and `:error`. The booleans `true` and `false` are also atoms: ```elixir iex> true == :true true iex> is_atom(false) true iex> is_boolean(:false) true ``` Elixir allows you to skip the leading `:` for the atoms `false`, `true` and `nil`. ## Strings Strings in Elixir are delimited by double quotes, and they are encoded in UTF-8: ```elixir iex> "hellö" "hellö" ``` > Note: if you are running on Windows, there is a chance your terminal does not use UTF-8 by default. You can change the encoding of your current session by running `chcp 65001` before entering IEx. You can concatenate two strings with the [`<>`](`<>/2`) operator: ```elixir iex> "hello " <> "world!" "hello world!" ``` Elixir also supports string interpolation: ```elixir iex> string = "world" iex> "hello #{string}!" "hello world!" ``` String concatenation requires both sides to be strings but interpolation supports any data type that may be converted to a string: ```elixir iex> number = 42 iex> "i am #{number} years old!" "i am 42 years old!" ``` Strings can have line breaks in them. You can introduce them using escape sequences: ```elixir iex> "hello ...> world" "hello\nworld" iex> "hello\nworld" "hello\nworld" ``` You can print a string using the [`IO.puts`](`IO.puts/1`) function from the `IO` module: ```elixir iex> IO.puts("hello\nworld") hello world :ok ``` Notice that the [`IO.puts`](`IO.puts/1`) function returns the atom `:ok` after printing. Strings in Elixir are represented internally by contiguous sequences of bytes known as binaries: ```elixir iex> is_binary("hellö") true ``` We can also get the number of bytes in a string: ```elixir iex> byte_size("hellö") 6 ``` Notice that the number of bytes in that string is 6, even though it has 5 graphemes. That's because the grapheme "ö" takes 2 bytes to be represented in UTF-8. We can get the actual length of the string, based on the number of graphemes, by using the [`String.length`](`String.length/1`) function: ```elixir iex> String.length("hellö") 5 ``` The `String` module contains a bunch of functions that operate on strings as defined in the Unicode standard: ```elixir iex> String.upcase("hellö") "HELLÖ" ``` ## Structural comparison Elixir also provides [`==`](`==/2`), [`!=`](`!=/2`), [`<=`](`<=/2`), [`>=`](`>=/2`), [`<`](``](`>/2`) as comparison operators. We can compare numbers: ```elixir iex> 1 == 1 true iex> 1 != 2 true iex> 1 < 2 true ``` But also atoms, strings, booleans, etc: ```elixir iex> "foo" == "foo" true iex> "foo" == "bar" false ``` Integers and floats compare the same if they have the same value: ```elixir iex> 1 == 1.0 true iex> 1 == 2.0 false ``` However, you can use the strict comparison operator [`===`](`===/2`) and [`!==`](`!==/2`) if you want to distinguish between integers and floats: ```elixir iex> 1 === 1.0 false ``` The comparison operators in Elixir can compare across any data type. We say these operators perform _structural comparison_. For more information, you can read our documentation on [Structural vs Semantic comparisons](`Kernel#module-structural-comparison`). Elixir also provides data-types for expressing collections, such as lists and tuples, which we learn next. When we talk about concurrency and fault-tolerance via processes, we will also discuss ports, pids, and references, but that will come on later chapters. Let's move forward.