Function Reference
Complete reference of all built-in Trill functions — string, number, list, date, and utility functions.
String Functions
upper(text) → string
Convert all characters to uppercase.
upper("hello") // "HELLO"lower(text) → string
Convert all characters to lowercase.
lower("HELLO") // "hello"trim(text) → string
Remove leading and trailing whitespace.
trim(" hello ") // "hello"trim_start(text) → string
Remove leading whitespace only.
trim_start(" hello ") // "hello "trim_end(text) → string
Remove trailing whitespace only.
trim_end(" hello ") // " hello"len(value) / length(value) → number
Return the length of a string or number of elements in a list.
len("hello") // 5
len([1, 2, 3]) // 3repeat(text, count) → string
Repeat a string count times.
repeat("ha", 3) // "hahaha"replace(text, from, to) → string
Replace all occurrences of from with to.
replace("hi there", "hi", "hello") // "hello there"slice(text, start, end) → string
Extract characters from index start (inclusive) to end (exclusive). Supports negative indices .
slice("hello", 1, 4) // "ell"
slice("hello", -3, -1) // "ll"substr(text, start, length) → string
Extract length characters starting at start.
substr("hello", 1, 3) // "ell"split(text, delimiter) → list
Split a string into a list of substrings.
split("a,b,c", ",") // ["a", "b", "c"]contains(text, substring) → boolean
Check if text contains substring.
contains("hello world", "world") // truestarts_with(text, prefix) → boolean
Check if text starts with prefix.
starts_with("hello", "he") // trueends_with(text, suffix) → boolean
Check if text ends with suffix.
ends_with("hello", "lo") // truereverse(value) → string or list
Reverse a string or list in place.
reverse("hello") // "olleh"
reverse([1, 2, 3]) // [3, 2, 1]pad_start(text, target_len, pad_char?) → string
Left-pad the string until it reaches target_len. Pads with pad_char (space by default).
pad_start("42", 5, "0") // "00042"
pad_start("hi", 5) // " hi"pad_end(text, target_len, pad_char?) → string
Right-pad the string until it reaches target_len.
pad_end("42", 5, "0") // "42000"concat(a, b, ...) → string
Concatenate all arguments as strings.
concat("hello", " ", "world") // "hello world"title(text) → string
Convert to title case — uppercase the first letter after any whitespace, -, or _.
title("hello world") // "Hello World"join(list, separator?) / join_list(list, separator?) → string
Join list elements into a string with optional separator.
join(["a", "b", "c"], ", ") // "a, b, c"
join(["a", "b", "c"]) // "abc"Number Functions
to_num(text) / number(text) → number
Parse a string into a number.
to_num("42") // 42
to_num("3.14") // 3.14to_str(value) / string(value) → string
Convert any value to its string representation.
to_str(42) // "42"
to_str(true) // "true"
to_str(nil) // ""floor(n) → number
Round down to the nearest integer.
floor(3.7) // 3
floor(-1.3) // -2ceil(n) / ceiling(n) → number
Round up to the nearest integer.
ceil(3.2) // 4
ceil(-1.3) // -1round(n) → number
Round to the nearest integer.
round(3.7) // 4
round(3.2) // 3abs(n) → number
Absolute value.
abs(-5) // 5min(a, b, ...) → number
Return the minimum of two or more values.
min(3, 7, 1, 9) // 1max(a, b, ...) → number
Return the maximum of two or more values.
max(3, 7, 1, 9) // 9clamp(value, lo, hi) → number
Clamp a value between lo and hi.
clamp(15, 0, 10) // 10
clamp(-5, 0, 10) // 0
clamp(7, 0, 10) // 7rand() → number
Random float between 0 and 1.
rand() // e.g., 0.472839rand(lo, hi) → number
Random integer between lo and hi (inclusive).
rand(1, 100) // e.g., 73List Functions
list(a, b, ...) → list
Create a list from individual arguments.
list(1, 2, 3) // [1, 2, 3]len(value) / length(value) → number
Return the number of elements in a list (or length of a string).
len([10, 20, 30]) // 3first(list) / first(string) → any
Return the first element of a list or character of a string.
first([10, 20, 30]) // 10
first("hello") // "h"last(list) / last(string) → any
Return the last element of a list or character of a string.
last([10, 20, 30]) // 30
last("hello") // "o"reverse(list) / reverse(string) → list or string
Reverse the order of a list or characters of a string.
reverse([1, 2, 3]) // [3, 2, 1]sort(list) → list
Sort a list by the string representation of its elements.
sort([3, 1, 2]) // [1, 2, 3]choice(list) → any
Pick a random element from the list.
choice(["rock", "paper", "scissors"]) // e.g., "paper"map(list, builtin_name) → list
Transform each element of a list by calling a built-in function on each item. The function is referenced by name as a string.
map(["hello", "world"], "upper") // ["HELLO", "WORLD"]filter(list, condition_name) → list
Keep only elements where a built-in condition function returns true. The function is referenced by name as a string.
filter([1, 2, 3, 4], "is_even") // calls is_even on eachjoin(list, separator?) / join_list(list, separator?) → string
Join list elements into a string with an optional separator.
join(["a", "b", "c"], ", ") // "a, b, c"Date / Time Functions
now(format?) → string
Return the current date and time. Uses strftime format — defaults to %Y-%m-%d %H:%M:%S.
now() // "2026-05-13 14:30:00"
now("%Y-%m-%d") // "2026-05-13"
now("%B %d, %Y at %I:%M %p") // "May 13, 2026 at 02:30 PM"today(format?) → string
Return the current date. Defaults to %Y-%m-%d.
today() // "2026-05-13"
today("%A, %B %d, %Y") // "Tuesday, May 13, 2026"date_add(date_string, days) → string
Add or subtract days from a date string.
date_add("2026-05-13", 7) // "2026-05-20"
date_add("2026-05-13", -3) // "2026-05-10"date_format(date_string, format) → string
Reformat a date string using a strftime format.
date_format("2026-05-13", "%A") // "Tuesday"strftime Format Specifiers
| Specifier | Meaning | Example |
|---|---|---|
%Y | 4-digit year | 2026 |
%y | 2-digit year | 26 |
%m | Zero-padded month | 05 |
%B | Full month name | May |
%b | Abbreviated month name | May |
%d | Zero-padded day of month | 13 |
%A | Full weekday name | Tuesday |
%a | Abbreviated weekday name | Tue |
%H | 24-hour, zero-padded | 14 |
%I | 12-hour, zero-padded | 02 |
%M | Minutes, zero-padded | 30 |
%S | Seconds, zero-padded | 00 |
%p | AM or PM | PM |
Utility Functions
if_then_else(condition, then_value, else_value) → any
Ternary conditional — returns then_value if the condition is truthy, otherwise else_value.
if_then_else(5 > 3, "yes", "no") // "yes"This is equivalent to the if then else expression but available as a callable function.
Template Variables
These built-in variables are always available in trigger replacements:
| Variable | Description | Example |
|---|---|---|
{{date}} | Current date | 2026-05-13 |
{{time}} | Current time | 14:30:00 |
{{datetime}} | Date and time | 2026-05-13 14:30:00 |
{{year}} | Current year | 2026 |
{{month}} | Current month (zero-padded) | 05 |
{{day}} | Current day (zero-padded) | 13 |
{{hour}} | Current hour | 14 |
{{minute}} | Current minute | 30 |
{{second}} | Current second | 00 |
{{weekday}} | Weekday name | Wednesday |
{{shortdate}} | Short date format | 05/13/2026 |
Trigger Arguments
When a trigger has argument mode enabled, these variables are available:
| Variable | Description | Example |
|---|---|---|
args | List of all arguments | args[0], args[-1] |
_arg_0, _arg_1, ... | Individual arguments | _arg_0 |
_args_len | Number of arguments | 3 |
Map and Filter Notes
map(list, name) and filter(list, name) accept a built-in function name as a string, not a lambda expression. The named function is called once per element with the current item.
For example, to convert all strings in a list to uppercase:
map(["hello", "world"], "upper")
// → ["HELLO", "WORLD"]To check if a condition holds for any element, you'd need a built-in that returns a boolean. Custom conditions as lambdas are not yet supported.