Built-in Functions

The engine supports a wide range of standard FEEL functions.

String Functions

Function	Parameters	Return Type	Description	Example
string	from: any	string	Converts a value to a string representation.	string(123) = "123"
string length	string: string	number	Returns the length of a string (number of characters).	string length("foo") = 3
upper case	string: string	string	Converts a string to uppercase.	upper case("hello") = "HELLO"
lower case	string: string	string	Converts a string to lowercase.	lower case("HELLO") = "hello"
substring	string: string, start: number, length?: number	string	Returns a substring starting at the given position.	substring("hello", 2, 3) = "ell"
substring before	string: string, match: string	string	Returns the substring before the first occurrence of match.	substring before("hello world", " ") = "hello"
substring after	string: string, match: string	string	Returns the substring after the first occurrence of match.	substring after("hello world", " ") = "world"
replace	input: string, pattern: string, replacement: string, flags?: string	string	Replaces occurrences of a pattern with a replacement string (supports regex).	replace("hello", "l", "L") = "heLLo"
contains	string: string, match: string	boolean	Returns true if the string contains the match substring.	contains("hello", "ell") = true
starts with	string: string, match: string	boolean	Returns true if the string starts with the match substring.	starts with("hello", "he") = true
ends with	string: string, match: string	boolean	Returns true if the string ends with the match substring.	ends with("hello", "lo") = true
string join	list: list<string>, delimiter?: string, prefix?: string, suffix?: string	string	Joins a list of strings with a delimiter.	string join(["a","b","c"], ",") = "a,b,c"
split	string: string, delimiter: string	list<string>	Splits a string using a delimiter (regex pattern).	split("a,b,c", ",") = ["a","b","c"]
matches	input: string, pattern: string, flags?: string	boolean	Returns true if the input matches the regex pattern.	matches("hello", "h.*o") = true

Number Functions

Function	Parameters	Return Type	Description	Example
abs	number: number	number	Returns the absolute value of a number.	abs(-10) = 10
ceiling	n: number, scale?: number	number	Rounds up to the nearest integer or specified scale.	ceiling(1.4) = 2
floor	n: number, scale?: number	number	Rounds down to the nearest integer or specified scale.	floor(1.6) = 1
round up	n: number, scale: number	number	Rounds up to the specified number of decimal places.	round up(1.234, 2) = 1.24
round down	n: number, scale: number	number	Rounds down to the specified number of decimal places.	round down(1.236, 2) = 1.23
round half up	n: number, scale: number	number	Rounds to the nearest value, rounding up on .5.	round half up(1.25, 1) = 1.3
round half down	n: number, scale: number	number	Rounds to the nearest value, rounding down on .5.	round half down(1.25, 1) = 1.2
decimal	n: number, scale: number	number	Returns the decimal representation with the specified scale.	decimal(1.5, 2) = 1.50
modulo	dividend: number, divisor: number	number	Returns the remainder of division.	modulo(10, 3) = 1
sqrt	number: number	number	Returns the square root of a number.	sqrt(16) = 4
exp	number: number	number	Returns e raised to the power of the number.	exp(1) ≈ 2.718
log	number: number	number	Returns the natural logarithm of a number.	log(10) ≈ 2.303
even	number: number	boolean	Returns true if the number is even.	even(4) = true
odd	number: number	boolean	Returns true if the number is odd.	odd(3) = true

List Functions

Function	Parameters	Return Type	Description	Example
list contains	list: list, element: any	boolean	Returns true if the list contains the element.	list contains([1,2,3], 2) = true
count	list: list	number	Returns the number of elements in a list.	count([1,2,3]) = 3
min	list: list<number>	number	Returns the minimum value in a list.	min([1,2,3]) = 1
max	list: list<number>	number	Returns the maximum value in a list.	max([1,2,3]) = 3
sum	list: list<number>	number	Returns the sum of all numbers in a list.	sum([1,2,3]) = 6
product	list: list<number>	number	Returns the product of all numbers in a list.	product([2,3,4]) = 24
mean	list: list<number>	number	Returns the arithmetic mean of a list of numbers.	mean([1,2,3]) = 2
median	list: list<number>	number	Returns the median value of a list of numbers.	median([1,2,3,4,5]) = 3
stddev	list: list<number>	number	Returns the standard deviation of a list of numbers.	stddev([2,4,7,5])
mode	list: list<number>	list<number>	Returns the mode (most frequent values) of a list.	mode([1,2,2,3]) = [2]
all	list: list<boolean>	boolean	Returns true if all elements in the list are true.	all([true, true]) = true
any	list: list<boolean>	boolean	Returns true if any element in the list is true.	any([false, true]) = true
sublist	list: list, start: number, length?: number	list	Returns a sublist starting at the given position.	sublist([1,2,3,4], 2, 2) = [2,3]
append	list: list, items...: any	list	Appends items to a list.	append([1,2], 3, 4) = [1,2,3,4]
concatenate	list: list, lists...: list	list	Concatenates multiple lists.	concatenate([1,2], [3,4]) = [1,2,3,4]
insert before	list: list, position: number, newItem: any	list	Inserts an element before the specified position.	insert before([1,3], 2, 2) = [1,2,3]
remove	list: list, position: number	list	Removes an element at the specified position.	remove([1,2,3], 2) = [1,3]
reverse	list: list	list	Reverses the order of elements in a list.	reverse([1,2,3]) = [3,2,1]
index of	list: list, match: any	list<number>	Returns a list of positions where the match is found.	index of([1,2,3,2], 2) = [2,4]
union	lists...: list	list	Returns the union of multiple lists (distinct values).	union([1,2], [2,3]) = [1,2,3]
distinct values	list: list	list	Returns a list with duplicate values removed.	distinct values([1,2,2,3]) = [1,2,3]
flatten	list: list	list	Flattens nested lists into a single list.	flatten([[1,2],[3,4]]) = [1,2,3,4]
sort	list: list, precedes?: function	list	Sorts a list using natural order or a comparison function.	sort([3,1,2]) = [1,2,3]
list replace	list: list, position: number, newItem: any	list	Replaces an element at the specified position.	list replace([1,2,3], 2, 5) = [1,5,3]

Date and Time Functions

Function	Parameters	Return Type	Description	Example
date	from: string	date	Creates a date from a string or from year/month/day components.	date("2023-01-15")
time	from: string	time	Creates a time from a string or from hour/minute/second components.	time("10:30:00")
date and time	from: string	date and time	Creates a date-time from a string or from date and time components.	date and time("2023-01-15T10:30:00")
duration	from: string	duration	Creates a duration from a string (ISO 8601 format).	duration("P1DT2H")
years and months duration	from: string	years and months duration	Creates a year-month duration from a string or date parameters.	years and months duration("P1Y2M")
day of year	date: date	number	Returns the day of the year (1-366).	day of year(date("2023-02-01"))
month of year	date: date	string	Returns the month name.	month of year(date("2023-02-01")) = "February"
week of year	date: date	number	Returns the week number of the year.	week of year(date("2023-02-01"))
last day of month	date: date	date	Returns the last day of the month for a given date.	last day of month(date("2023-02-01"))
today	``	date	Returns the current date.	today()
now	``	date and time	Returns the current date and time.	now()

Temporal Relation Functions

Function	Parameters	Return Type	Description	Example
before	point1: any, point2: any	boolean	Returns true if point1 is before point2.	before(date("2023-01-01"), date("2023-01-02")) = true
after	point1: any, point2: any	boolean	Returns true if point1 is after point2.	after(date("2023-01-02"), date("2023-01-01")) = true
meets	interval1: range, interval2: range	boolean	Returns true if interval1 ends exactly when interval2 starts.	meets([1..5], [5..10])
met by	interval1: range, interval2: range	boolean	Returns true if interval2 ends exactly when interval1 starts.	met by([5..10], [1..5])
overlaps	interval1: range, interval2: range	boolean	Returns true if the intervals overlap.	overlaps([1..5], [3..7])
overlaps before	interval1: range, interval2: range	boolean	Returns true if interval1 overlaps and ends before interval2 ends.	overlaps before([1..5], [3..7])
overlaps after	interval1: range, interval2: range	boolean	Returns true if interval1 overlaps and starts after interval2 starts.	overlaps after([3..7], [1..5])
finishes	point: any, interval: range	boolean	Returns true if point/interval finishes at the end of interval.	finishes(5, [1..5])
finished by	interval: range, point: any	boolean	Returns true if interval is finished by point/interval.	finished by([1..5], 5)
includes	interval: range, point: any	boolean	Returns true if interval includes point/interval.	includes([1..10], 5)
during	point: any, interval: range	boolean	Returns true if point/interval is during interval.	during(5, [1..10])
starts	point: any, interval: range	boolean	Returns true if point/interval starts at the start of interval.	starts(1, [1..5])
started by	interval: range, point: any	boolean	Returns true if interval is started by point/interval.	started by([1..5], 1)
coincides	point1: any, point2: any	boolean	Returns true if two points/intervals coincide.	coincides([1..5], [1..5])

Context Functions

Function	Parameters	Return Type	Description	Example
get value	context: context, key: string	any	Gets a value from a context by key.	get value({a: 1}, "a") = 1
get entries	context: context	list<context>	Returns a list of key-value pairs from a context.	get entries({a: 1, b: 2})
context	entries: list	context	Creates a context from a list of key-value pairs.	context([{key: "a", value: 1}])
context put	context: context, key: string, value: any	context	Adds or updates a key-value pair in a context.	context put({a: 1}, "b", 2)
context merge	contexts: list<context>	context	Merges multiple contexts into one.	context merge([{a: 1}, {b: 2}])

Other Functions

Function	Parameters	Return Type	Description	Example
is	value: any, type: string	boolean	Returns true if value is of the specified type.	is(5, "number") = true
range	from: string	range	Creates a range from a string representation.	range("[1..10]")
number	from: string, grouping separator?: string, decimal separator?: string	number	Converts a string to a number with optional separators.	number("1,000.50", ",", ".")