Types

FEEL is a dynamically typed language. The following types are supported.

Primitive types

Type	Examples	Notes
number	1, 3.14, -42, 1e6	Decimal128 precision
string	"hello", ""	Unicode, code-point length
boolean	true, false
null	null	Represents absence of value

Temporal types

Type	Example	Properties
date	date("2024-01-15")	.year, .month, .day, .weekday
time	time("10:30:00")	.hour, .minute, .second, .time zone, .time offset
date and time	date and time("2024-01-15T10:30:00")	all of the above + .date, .time, .offset
years and months duration	duration("P1Y2M")	.years, .months
days and time duration	duration("P1DT2H30M")	.days, .hours, .minutes, .seconds

Collection types

Type	Example
list	[1, 2, 3], []
context	{name: "Alice", age: 30}
range	[1..5], (0..100)

Function type

function(x) x + 1
function(a: number, b: number) a + b

Type checking

Use instance of to check types at runtime:

1 instance of number                    // true
date("2024-01-01") instance of date     // true
[1,2,3] instance of list<number>        // true
{a:1} instance of context<a: number>   // true
null instance of Null                   // true
42 instance of Any                      // true

Null propagation

Most operations return null when given null inputs:

null + 1        // null
null > 5        // null
not(null)       // false (special case)

Equality is the exception:

null = null     // true
null = 1        // false