Built-in native functions

All of these work with or without the ton. prefix (see Language basics).

Core

Function	Description
`print(x)`	Prints a value to stdout
`type(x)`	Returns the type name of a value as a string
`str(x)`	Converts a value to string
`num(x)`	Converts a value to number (`0` if it can't be parsed)
`format(template, ...args)`	Replaces each `{}` in `template` with the matching argument (see String formatting)
`json(x)`	Converts a value (array, dict, or scalar) to a JSON string
`assert(cond, [msg])`	Throws (catchable) if `cond` is falsy
`input([prompt])`	Prints an optional prompt, reads and returns one line from stdin
`readfile(path)`	Reads a file's content as `ton.html` (resolved relative to the script's directory too)
`writefile(path, content)`	Writes (overwriting) a file with `content`; returns whether it succeeded

Math

Function	Description
`sqrt(x)`, `pow(x, y)`, `abs(x)`	Square root, power, absolute value
`floor(x)`, `ceil(x)`, `round(x)`	Rounding
`min(...)`, `max(...)`	Smallest/largest of any number of arguments
`random()`	A float in `[0, 1)`
`random(max)`	An integer in `[0, max)`
`random(min, max)`	An integer in `[min, max)`

Strings

Function	Description
`len(s)`	Length
`upper(s)`, `lower(s)`	Case conversion
`trim(s)`	Strips leading/trailing whitespace
`split(s, sep)`	Splits into a `ton.array` of strings
`join(arr, sep)`	Joins an array into a string (see also under Arrays)
`replace(s, search, repl)`	Replaces every occurrence of `search` with `repl`
`substring(s, start, [length])`	Extracts a substring
`contains(s, sub)`	Whether `sub` occurs in `s`
`indexOf(s, sub)`	Index of the first occurrence, or `-1`
`s[i]`	The character at index `i`, as a 1-character string (read-only — see Arrays)

Arrays

Function	Description
`len(arr)`	Number of elements
`push(arr, v)`	Appends a value (mutates in place)
`pop(arr)`	Removes and returns the last element
`shift(arr)`	Removes and returns the first element
`unshift(arr, v)`	Inserts a value at the front
`slice(arr, start, [end])`	Returns a new sub-array
`join(arr, sep)`	Joins elements into a string
`sort(arr)`	Sorts in place (numeric or alphabetical) and returns it
`reverse(arr)`	Reverses in place and returns it
`contains(arr, item)`	Whether `item` is an element (structural equality)
`indexOf(arr, item)`	Index of the first matching element, or `-1`
`map(arr, fn)`	New array of `fn(element)` for each element
`filter(arr, fn)`	New array keeping only elements where `fn(element)` is truthy
`reduce(arr, fn, initial)`	Folds the array via `fn(accumulator, element)`
`find(arr, fn)`	First element where `fn(element)` is truthy, or `nil`
`any(arr, fn)`	`true` if `fn(element)` is truthy for at least one element
`all(arr, fn)`	`true` if `fn(element)` is truthy for every element

Dicts

Function	Description
`len(d)`	Number of keys
`keys(d)`	Array of keys, in insertion order
`values(d)`	Array of values, in insertion order
`has(d, key)`	Whether `key` exists
`json(d)`	JSON-encodes the dict

HTTP server

Function	Description
`get(path, fn)`	Registers a GET route (see Local server)
`post(path, fn)`	Registers a POST route
`serve(port)` / `serve(port, content)`	Starts the local HTTP server

Added in beta-2.0.0 — every one of them can also be called with method syntax (arr.sum(), s.padStart(3, "0")).

Conversions & misc

Function	Description
`int(x, [base])`	Integer part of a number, or parse a string (`int("ff", 16)` is `255`)
`float(x)`	Parse a string as a number (errors on garbage, unlike `num`)
`bool(x)`	`true`/`false` according to truthiness
`fixed(x, [digits=2])`	Number to string with a fixed number of decimals
`round(x, [digits])`	Rounds, optionally to some decimals
`repr(x)`	Like `str`, but strings come back quoted
`isinstance(obj, Class)`	Whether `obj` is an instance of `Class` or of a subclass
`copy(x)` / `deepcopy(x)`	Shallow / recursive copy of an array, dict or object
`clamp(x, lo, hi)`, `sign(x)`	Number helpers
`exit([code])`	Stops the script immediately
`print(a, b, ...)`	`print` is also a function value, printing its arguments separated by spaces

Arrays

Function	Description
`range(end)`, `range(start, end, [step])`	Array of numbers, `end` excluded
`sum(arr)`, `avg(arr)`	Sum / mean of numbers
`min(arr)`, `max(arr)`	`min`/`max` also accept a single array
`sorted(arr, [key])`	Sorted copy; `key(x)` gives what to sort by: `sorted(words, w => len(w))`
`sort(arr, [compare])`	In place; `compare(a, b)` returns a negative number (or `true`) when `a` comes first
`forEach(arr, fn)`	Calls `fn(item)` (or `fn(item, index)`) for each element
`findIndex(arr, fn)`	Index of the first match, or `-1`
`count(arr, valueOrFn)`	How many elements equal a value / match a predicate (also counts substrings)
`flatMap(arr, fn)`	`map` then flatten one level
`unique(arr)`	Copy without duplicates (first occurrence kept)
`flatten(arr, [depth=1])`	Flattens nested arrays
`zip(a, b, ...)`	`[[a0, b0], [a1, b1], ...]`
`enumerate(arr)`	`[[0, a0], [1, a1], ...]`
`chunk(arr, size)`	Splits into arrays of `size` elements
`groupBy(arr, fn)`	Dict of arrays, grouped by `fn(item)`
`first(arr)`, `last(arr)`	First / last element, or `nil`
`insert(arr, index, value)`, `removeAt(arr, index)`	Insert / remove at a position
`remove(arr, value)`	Removes the first equal element; `remove(dict, key)` removes a key
`clear(x)`, `isEmpty(x)`	Empty an array/dict; test emptiness
`lastIndexOf(x, item)`	Last position in an array or string, or `-1`
`reduce(arr, fn)`	Without an initial value, starts from the first element

Dicts

keys, values, items, has and len also work on objects (their fields).

Strings

Function	Description
`startsWith(s, p)`, `endsWith(s, p)`	Prefix / suffix test
`padStart(s, width, [fill])`, `padEnd(...)`	Pad to a width
`repeat(s, n)`	Repeat a string (or an array)
`chars(s)`, `lines(s)`	Split into characters / lines
`capitalize(s)`	First letter in upper case
`reverse(s)`	`reverse` now also reverses a string
`ord(c)`, `chr(n)`	Character code and back