Literals

Fauna Query Language (FQL) supports literal syntax for Numbers, Boolean values, Null, Strings, Arrays, Objects, and Functions.

Boolean

A Boolean is a logical expression that evaluates to true or false.

The Boolean literals are true and false.

Null

The Null literal represents the absence of a value. In Boolean expressions, null evaluates to false.

The Null literal is null.

Number

A Number is a base 10 Int, decimal, or exponential.

Underscores can be used as separators instead of commas to improve readability but aren’t significant otherwise.

Integer

An Int literal starts with a nonzero digit and don’t include a fractional or exponential part. A negative integer literal is preceded by the - character.

10
-250
1_000_000

Integer literals can have the following base representation:

Base	Example
2	`0b1001`
8	`0o123`
10	`12345`
16	`0x12a3`

Decimal

A decimal literal includes a fractional part. Internally, these are handled as Doubles.

1.0
0.1

Exponential

E-notation is used for a decimal exponential literal: <decimal>e | E<exponent>:

1.2e23
3.4e-15

where,

<decimal> is the base integer.
e or E separator indicates an exponential literal.
<exponent> is the signed integer exponent.

String

A String literal is a sequence of single-quoted string values or double-quoted interpolated string values from the FQL-supported character set, and terminated by null.

Single-quoted Strings can include the " and # characters.

Double-quoted Strings can include the ' character.

Interpolated string

Double-quoted Strings support expression interpolation using the #{<expr>} character sequence, where <expr> is an FQL expression:

"Alice is #{3 + 2} years old."

"Alice is 5 years old."

See the escaped characters section for a list of escaped characters.

Heredoc string

A heredoc String is a way to write a string that spans multiple lines, enclosing the string with a beginning and ending user-defined token:

<<+TOKEN
  A multiline string
    with leading
      whitespaces
TOKEN

<<-END
A multiline string
  with leading
      whitespaces
END

The token, on a line by itself, terminates the String.

On rendering, whitespace is removed from form each line, maintaining the same relative indentation for each line.

Heredoc strings support interpolation:

let weather = "overcast with occasional showers"
<<+EOS
  Hello.
    Today is #{weather}
EOS

<<-END
  Hello.
    Today is overcast with occasional showers
END

To declare a String with variables but without doing interpolation, precede the String with a token in the format <<-TOKEN:

<<-ASIS
str => "Hello #{str}"
ASIS

<<-END
  str => "Hello #{str}"
END

You might want to avoid interpolation when defining a Function body, for example. The #{str} variable executes in the context of the function instead of when the string is rendered.

Array

Arrays group items and are represented as a comma-separated list of literals or expressions enclosed by [ ]:

["a", 1 + 1, if (true) "true" else "false", null]

[
  "a",
  2,
  "true",
  null
]

Array members can be accessed individually using a single variable. Members are indexed left to right, starting with 0. In the example, the "a" member is Array element 0 and the null member is array element 3:

let array = ["a", 1 + 1, if (true) "true" else "false", null]
[ array[0], array[3]]

[
  "a",
  null
]

Object

An Object is represented as a key:value pair enclosed by { }, or field:value pair when referring to schema entities.

{ "a": 1 }

An object can hold multiple, comma-separated key:value pairs:

{
  "a": 1,
  b: 2
}

Key or field names can be identifiers or String literals:

Anonymous function

An anonymous function is represented using the short-form, JavaScript-like arrow function syntax:

([parameter[, parameter]]) => {[statement [statement … ]] expression [expression … ]}

Or, simplified:

(parameter) => { expression }

If the function has only one parameter, () can be omitted around the parameter.

If the function body has only a single expression, the {} block delimiter can be omitted.

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