Built in functions

A complete list of currently supported functions.

These function can be used in lambda and script expressions

Type conversion

With a few exceptions every type can be converted to every other type.

Bool

bool(a_value) -> true|false

Integer

int(value) -> integer

If value is a float, then int(value) is equivalent to trunc(value)

Float

float(value) -> float

String

string(val) -> string

If val is a list:

String

string(list) -> string

Converting a list into a string with string is equivalent to

list_join(',', list_of_strings(List))

Converts every entry of List to a string first and then joins the resulting list with a comma.

[1,2,3] => ['1', '2', '3'] => '1,2,3'

Type checks

Function
`is_string(Data)` -> bool
`is_integer(Data)` -> bool
`is_int(Data)` -> bool
`is_float(Data)` -> bool
`is_number(Data)` -> bool
`is_list(Data)` -> bool
`is_duration(Data)` -> bool
`is_boolean(Data)` -> bool
`is_bool(Data)` -> bool

Time functions

Every data_point in faxe contains a field called ts, which holds a UTC timestamp in milliseconds.

Function	Description
`now()` -> integer	returns an utc timestamp in milliseconds
`dt_parse(ts, formatstring)` -> integer	used to parse a datetime string to the internal format, see datetime-parsing for details
`to_iso8601(ts)` -> string	converts the timestamp to an ISO8601 datetime string
`to_rfc3339(ts)` -> string	converts the timestamp to an RFC3339 datetime string
`from_duration(ts)` -> integer	converts a duration to it's millisecond equivalent
`millisecond(ts)` -> integer	milliseconds within the second [0, 999]
`second(ts)` -> integer	second within the minute [0, 59]
`minute(ts)` -> integer	minute within the hour [0, 59]
`hour(ts)` -> integer	hour within the day [0, 23]
`day(ts)` -> integer	day within the month [1, 31]
`day_of_week(ts)` -> integer	the weekday with week [1, 7] 1 is monday
`week(ts)` -> integer	isoweek-number within year [1, 53]
`month(ts)` -> integer	month within the year [1, 12]
`time_align(ts, duration)` -> integer	align the given timestamp to duration

Examples:

lambda: hour("ts") >= 8 AND hour("ts") < 19

The above expression evaluates to true if the hour of the day for the data point falls between 08:00 and 19:00.

lambda: time_align("ts", 3m)

Will align every timestamp (ts) to a multiple of the 3 minutes within an hour (ie: 00:00, 00:03, 00:06, ...)

Math functions

Function	Description
`abs(x)` -> number
`acos(x)` -> float
`acosh(x)` -> float
`asin(x)` -> float
`asinh(x)` -> float
`atan(x)` -> float
`atan2(y, x)` -> float
`atanh(x)` -> float
`ceil(x)` -> float
`cos(x)` -> float
`cosh(x)` -> float
`exp(x)` -> float
`floor(x)` -> float
`fmod(x, y)` -> float
`log(x)` -> float
`log10(x)` -> float
`log2(x)` -> float
`max(x, y)` -> number
`max(list)` -> number
`min(x, y)` -> number
`min(list)` -> number
`pi() -> float`	gives pi
`pow(x, y)` -> float
`round(x)` -> integer	round a number to an integer
`round_float(x, precision)` -> float	round a float (x) with the given precision
`trunc(x)` -> integer	Returns an integer by truncating a number
`sin(x)` -> float
`sinh(x)` -> float
`sqrt(x)` -> float
`tan(x)` -> float
`tanh(x)` -> float

String functions

String positions start with index 0.

Function	Description
`str_at(x, pos)` -> string/undefined	Returns the grapheme in the position of the given utf8 string. If position is greater than string length, then it returns undefined. Negative offsets count back from the end of the string.
`str_capitalize(x)` -> string	Converts the first character in the given string to uppercase and the remaining to lowercase
`str_concat(string1, string2)` -> string	Concatenate 2 strings.
`str_concat([string1, string2, ...])` -> string	Concatenate a list of strings.
`str_contains(x, contents)` -> bool	Check if string contains any of the given contents
`str_downcase(x)` -> string	Convert all characters on the given string to lowercase
`str_enclose(Wrapper, StringOrList)` -> string or list	Prepend and append Wrapper to a string or each entry of a list of strings
`str_ends_with(x, suffix)` -> string	Returns true if string ends with suffix, otherwise false.
`str_ends_with_any(x, suffixes)` -> string	Returns true if string ends with any of the suffixes given, otherwise false.
`str_eqi(x,y)` -> bool	Compares strings case insensitively
`str_first(x)` -> string/undefined	Returns the first grapheme from an utf8 string, undefined if the string is empty
`str_last(x)` -> string/undefined	Returns the last grapheme from an utf8 string, undefined if the string is empty
`str_length(x)` -> int	Returns the number of unicode graphemes in an utf8 string
`str_lstrip(x)` -> string	Returns a string where leading Unicode whitespace has been removed
`str_lstrip(x, char)` -> string	Returns a string where leading char have been removed
str_pad_leading/2
str_pad_leading/3
str_pad_trailing/2
str_pad_trailing/3
`str_quote(string)` -> string	Enclose a string with double quotes.
`str_replace(x, patt, repl)` -> string	Returns a new string based on subject by replacing the parts matching pattern by replacement. Both `pattern` and `replace` may be of type string or list.
str_replace_leading/3	Replaces all leading occurrences of match by replacement of match in string.
str_replace_trailing/3	Replaces all trailing occurrences of match by replacement of match in string.
`str_replace_prefix(x, match, repl)` -> string	Replaces prefix in string by replacement if it matches match. Returns the string untouched if there is no match. If match is an empty string (""), replacement is just prepended to string.
`str_replace_suffix(x, match, repl)` -> string	Replaces suffix in string by replacement if it matches match. Returns the string untouched if there is no match. If match is an empty string (""), replacement is just appended to string.
`str_reverse(x)` -> string	Reverses the given string.
`str_rstrip(x)` -> string	Returns a string where trailing Unicode whitespace has been removed
`str_rstrip(x, char)` -> string	Returns a string where trailing char have been removed
`str_slice(x, start, len)` -> string	Returns a substring starting at the offset given by the first, and a length given by the second param, if offset is negative, count back from end of string.
str_split/1
str_split/2
str_split/3
str_split_at/2
str_split_by_any/2
str_split_by_any/3
str_split_by_re/2
str_split_by_re/3
`str_starts_with(x, pre)` -> bool	Returns true if string starts with Prefix
`str_starts_with_any(x, prefixes)` -> bool	Returns true if string starts with any of the prefixes given, otherwise false.
`str_strip(x)` -> string	Returns a string where leading/trailing Unicode whitespace has been removed
`str_strip(x, char)` -> string	Returns a string where leading/trailing char have been removed
`str_upcase(x)` -> string	Convert all characters on the given string to uppercase
`str_repeat_replace(string, pattern, replaceList)` -> list	Given a string, a pattern and a list of strings, produces a new list of strings by `duplicating` string `length(replaceList)` times, while replacing every occurance of `pattern` with the corresponding entry from `replaceList`. If `pattern` is not found in `string`, it will be left untouched and simply duplicated.

Lists

Function	Description	Example
`head(List)` -> any	Returns the head, or the first element, of list List.	head("data.lines")
`nth(Integer, List)` -> any	Returns the nth element from list List, list indices start with 1.	nth(N, "data.lines")
`nthtail(Integer, List)` -> any	Returns the Nth tail of List, that is, the sublist of List starting at N+1 and continuing up to the end of the list.	nthtail(N, "data.lines")
`list_append(List1, List2)` -> list	Returns a new list, which is made from the elements of List1 followed by the elements of List2.	list_append(['a', 'b', 'c'], [1, 2, 4])
`list_delete(Elem, List)` -> list	Returns a copy of List, where the first element matching Elem is deleted, if there is such an element.	list_delete(2, [1, 2, 4]) -> [1, 4]
`list_last(List)` -> any	Returns the last element from List.
`list_max(List)` -> any	Returns the first element of List that compares greater than or equal to all other elements of List.	list_max([1, 2, 4]) -> 4
`list_min(List)` -> any	Returns the first element of List that compares less than or equal to all other elements of List.	list_min([1, 2, 4]) -> 1
`list_reverse(List)` -> list	Returns a list with the elements in List1 in reverse order.	list_reverse([1, 2, 4]) -> [4, 2, 1]
`list_sort(List)` -> list	Returns a list containing the sorted elements of List1.	list_sort([4, 5, 1, 2, 4]) -> [1, 2, 4, 4, 5]
`list_subtract(List1, List2)` -> list	Returns a new list List3 that is a copy of List1, subjected to the following procedure:for each element in List2, its first occurrence in List1 is deleted.
`list_sum(List)` -> number	eturns the sum of the elements in List.
`list_unique(List)` -> list	Returns a new list with only unique values from List.	list_unique("data.lines")
`list_usort(List)` -> list	Returns a list containing the sorted elements of List1 where all except the first element of the elements comparing equal have been deleted.
`list_join(List)` -> string	Equivalent to list_join(',', List).	list_join("data.lines")
`list_join(Separator, List)` -> string	Join a list of strings with a separator string.	list_join('-', "data.lines")
`list_of_strings(List)` -> list	Convert every entry of a list to a string and return the list of strings.	list_of_strings("data.lines")
`sublist(List, Len))` -> list	Returns the sublist of List1 starting at position 1 and with (maximum) Len elements. It is not an error for Len to exceed the length of the list, in that case the whole list is returned.
`sublist(List, Start, Len))` -> list	Returns the sublist of List1 starting at Start and with (maximum) Len elements. It is not an error for Start+Len to exceed the length of the list.

Lists and Maps (jsn)

Functions marked with a star (*), can work directly on json strings representing lists or objects (maps in faxe). For example, you can feed a json object string to map_get to get a value out of the json object:

def json_map = '{"key1": "value1", "key2": "value2"}'

def key1_val = e:map_get('key1', json_map)
%% 'value1'

To use a json string in other functions listed here, you have to convert them to faxe's internal format first, using from_json_string:

def json_map = '{"key1": "value1", "key2": "value2", "key3": "value3"}'
%% first convert to faxe's internal format
def internal_map = e: from_json_string(json_map)
def has_key3 = e:member('key3', internal_map)
%% true

Function	Description	Example
*`from_json_string(String)` -> faxe map or list	Convert a valid json string into faxe's internal data-structure.	from_json_string('{"a":"b"}')
`to_json_string(String)` -> string	Convert faxe's internal data-structure into a json string.	to_json_string("data.struct")
`size(ListOrMap)` -> integer	Get the number of entries in a list or map.	size("data.lines")
`member(Ele, ListOrMap)` -> bool	Check for list/set membership of a value, or when used with a map, check if Ele is a key in the map.
`not_member(Ele, ListOrMap)` -> bool
*`map_get(Key, Map)` -> any	Get a value from a map, equivalent to `map_get(Key, Map, 'undefined')`.	map_get("topic", '{"data/temp/val1": "temp"}')
*`map_get(Key, Map, Default)` -> any	Get a value from a map, `Default` is returned, if the key is not present in map.	map_get("topic", '{"data/temp/val1": "temp"}', 'no_match')
*`select(Key, Jsn)` -> list	Select every value with the path `Key` from a json-array.	See description below.
*`select(Key, Where, Jsn)` -> list	Select every value with the path `Key` and conditions `Where` from a json-array. Elements that do not meet the given conditions are filtered out.	See description below.
*`select_all(Key, Where, Jsn)` -> list	Select every value with the path `Key` and conditions `Where` from a json-array. The list of `Where` conditions are `OR`ed in this case, so there is a select operation for every entry in `Where`	See description below.
*`select_first(Key, Jsn)` -> any	Select the first value with the path `Key` from a json-array.	See description below.
*`select_first(Key, Where, Jsn)` -> any	Select the first value with the path `Key` and conditions `Where` from a json-array.	See description below.
*`select_any(Key, Where, Jsn)` -> any	Select the first value with the path `Key` that is found with any of the `Where` conditions from a json-array.	See description below.

select, select_first, select_any

With these functions we can select values from a json-array like datastructure, meaning an array of - possibly nested - json objects.

def fruits =
'[
  {"color":  "orange", "name": "orange", "peel":  true}, 
  {"color":  "orange", "name": "mandarin", "peel":  true}, 
  {"color":  "orange", "name": "peach", "peel":  false},
  {"color":  "orange", "name": "navel-orange", "peel":  true},
  {"color":  "yellow", "name": "lemon", "peel":  true}
]'

The Where parameter in select functions is a list of tuples.

e: select('name', [{'peel', true}], fruits)

e: select_first('name', [{'color', 'orange'}, {'peel', false}], fruits)

The first example above would select the names of all fruits, that have a 'peel' value of true: ['orange', 'mandarin', 'navel-orange', 'lemon']. The second example selects the first name with 'color' orange and the 'peel' value false: 'peach'.

Besides an exact match in the Where parameters, we can also use a regular expression:

e: select('name', [{'regex', 'name', 'orange$'}], fruits)

Results in ['orange', 'navel-orange'].

Misc

Function	Description	Example
`defined(Key::string)` -> bool	whether the given Key is defined in the current data-item
`undefined(Key::string)` -> bool	whether the given Key is NOT defined in the current data-item
`empty(Key::string)` -> bool	whether the given Key points to an empty or not defined value, empty means an empty string or an empty list or tuple	empty("data.topic") -> false
`topic_part(TopicString, PartIndex, [Seperator])` -> string	extract a part from a topic string, Separator defaults to '/', the index of the first part is `1` not 0	topic_part('this/is/mytopic', 2) -> 'is'
`random(N::int)` -> integer	generate a random integer uniformly distributed between 1 and N
`random(N::int, M::int)` -> integer	generate a random integer uniformly distributed between N and M
`random_real(N)` -> float	generate a random float between 0.0 and 1.0, that gets multiplied by N
`random_normal()` -> float	generate a standard normal deviate float (that is, the mean is 0 and the standard deviation is 1)
`random_latin_string(Length)` -> string	Returns a random string of size Length, consisting of latins `[a-zA-Z]` and digits `[0-9]`.
`base64_encode(String)` -> string	Encode a string to base64 format.
`base64_decode(String)` -> string	Decode a base64 encoded string.
`crc32(String)` -> string	Computes the crc32 (IEEE 802.3 style) checksum for the given string.
`phash(Any)` -> integer	Portable hash function, that outputs an integer in the range 0..2^27-1
`uuidv4()` -> string	Get a strong v4 UUID string (using crypto/openssl)
`env(Key::string)` -> string \| false	Get the value from an OS-ENV variable, if not found, returns `false`. Note that the value returned (except false) is always as string.	env('FAXE_MQTT_HOST') -> '127.0.0.1'
`env(Key::string, Default)` -> string \| any	Get the value from an OS-ENV variable, if not found, returns `Default`. Note that the value returned (except Default) is always as string.	env('FAXE_MQTT_HOS', '127.0.0.1') -> '127.0.0.1'
`envs()` -> map	Get a map of all OS-ENV variables. All keys and values are strings.
`mem` values are set with the mem node
`ls_mem(Key)` -> any	get the single value associated with Key from the flow-memory
`ls_mem_list(Key)` -> any	get the list value associated with Key from the flow-memory
`ls_mem_set(Key)` -> any	get the set value associated with Key from the flow-memory

Conditional functions

Special if function

If

In DFS if is not a language construct, but a function with 3 parameters. The if function’s return type is the same type as its second and third arguments.

if(condition, true expression, false expression)

Returns the result of its operands depending on the value of the first argument.

Examples:

|eval(lambda: if("field.val1" > threshold AND "field.val1" != 0, 'true', 'false'))
.as('value')

The value of the field value in the above example will be the string true or false, depending on the condition passed as the first argument.

|eval(lambda: if(is_float("data.duration_ms"), trunc("data.duration_ms" * 1000), "data.duration_ms"))
.as('value')

Both expressions (2nd and 3rd parameter) may also be arbitrarily complex. In this example, if the condition returns true, data.duration_ms will be mulitplied be 1000 and then truncated to an integer. If the condition returns false, just the value of data.duration_ms will be returned.