#Standard library

Builtins and reserved words can be removed within a major version. One marked for removal is deprecated in a minor release and removed no earlier than the next one. While deprecated it keeps working, and the parser warns on the line that uses it (WARN line <n> in the status bar, full text in the Explain pane). Removals are listed in the release notes with their replacement. See Compatibility for what the version number covers elsewhere.

RTS provides a small standard library that covers common request needs without enabling file writes or network access. It keeps expressions small, readable, and predictable. The standard library is available as rts; stdlib remains as a deprecated alias. Core helpers and namespaces (crypto, base64, url, time, json, headers, query, encoding) are also exposed at top level for convenience. text, list, dict, and math are available only under rts.

##Core helpers

• rts.fail(msg) stops evaluation and returns an error message.
• rts.len(x) returns the length of a string, list, or dict.
• rts.contains(container, value) applies the same membership relation as value in container.
• rts.match(pattern, text) applies a regular expression to text and returns true when it matches.
• rts.str(x) converts a value to a string, using JSON for lists and dicts.
• rts.num(x[, def]) converts a value to a number, or returns def when conversion fails.
• rts.int(x[, def]) converts a value to an integer, or returns def when conversion fails.
• rts.bool(x[, def]) converts a value to a bool, or returns def when conversion fails.
• rts.typeof(x) returns the type name.
• rts.uuid() generates a UUID and requires random generation to be enabled.

##Crypto helpers

• rts.crypto.sha256(text) returns a hex encoded SHA-256 digest.
• rts.crypto.hmacSha256(key, text) returns a hex encoded HMAC-SHA256 digest.

##Encoding and URL helpers

• rts.base64.encode(x) encodes a string to base64.
• rts.base64.decode(x) decodes a base64 string.
• rts.encoding.hex.encode(x) encodes a string to hex.
• rts.encoding.hex.decode(x) decodes a hex string.
• rts.encoding.base64url.encode(x) encodes a string to base64url (no padding).
• rts.encoding.base64url.decode(x) decodes a base64url string.
• rts.url.encode(x) percent encodes a string for URL use.
• rts.url.decode(x) decodes a percent encoded string.

##Time helpers

• rts.time.nowISO() returns the current time in ISO 8601 format.
• rts.time.nowUnix() returns the current time as unix seconds.
• rts.time.nowUnixString() returns the current time as a decimal unix seconds string.
• rts.time.nowUnixMs() returns the current time as unix milliseconds.
• rts.time.format(layout) formats the current time with the given layout string.
• rts.time.parse(layout, value) parses the time string and returns unix seconds (fractional).
• rts.time.formatUnix(ts, layout) formats a unix timestamp with the given layout.
• rts.time.addUnix(ts, secondsOrDuration) adds seconds (number) or a duration string to a unix timestamp.
• rts.time.duration(value) parses a duration string (including d and w) and returns seconds.

##JSON helpers

• rts.json.file(path) reads and parses JSON using the request base directory (only when file access is enabled).
• rts.json.parse(text) parses a JSON string into RestermScript values.
• rts.json.stringify(value[, indent]) converts a value to JSON text. indent can be a string or a number (0-32).
• rts.json.get(value[, path]) returns the value at a dot or [index] path (optional leading $) and returns null when missing.
• rts.json.has(value, path) returns true when a value exists at the path.

##Text helpers

• rts.text.lower(s) returns a lowercased string.
• rts.text.upper(s) returns an uppercased string.
• rts.text.trim(s) trims leading and trailing whitespace.
• rts.text.split(s, sep) splits a string into a list.
• rts.text.join(list, sep) joins list items with a separator (items may be strings, numbers, or bools).
• rts.text.replace(s, old, new) replaces all occurrences of old with new.
• rts.text.startsWith(s, prefix) returns true when a string starts with prefix.
• rts.text.endsWith(s, suffix) returns true when a string ends with suffix.

##List helpers

• rts.list.append(list, item) returns a new list with item appended.
• rts.list.concat(a, b) returns a new list with b appended to a.
• rts.list.sort(list) returns a sorted copy (numbers or strings only).
• rts.list.map(list, fn) returns a new list with fn(item) applied to each value.
• rts.list.filter(list, fn) returns a new list of values where fn(item) is truthy.
• rts.list.any(list, fn) returns true if any value makes fn(item) truthy.
• rts.list.all(list, fn) returns true if all values make fn(item) truthy.
• rts.list.slice(list, start[, end]) returns a slice of the list.
• rts.list.unique(list) returns a list of unique primitive values.

##Dict helpers

• rts.dict.keys(dict) returns a sorted list of keys.
• rts.dict.values(dict) returns values ordered by sorted keys.
• rts.dict.items(dict) returns a list of {key, value} entries ordered by key.
• rts.dict.set(dict, key, value) returns a new dict with key set.
• rts.dict.merge(a, b) returns a new dict with b applied over a.
• rts.dict.remove(dict, key) returns a new dict without key.
• rts.dict.get(dict, key[, def]) returns def or null when missing.
• rts.dict.has(dict, key) returns true when a key exists.
• rts.dict.pick(dict, keys) returns a dict with the specified keys.
• rts.dict.omit(dict, keys) returns a dict without the specified keys.

These helpers use keys exactly as written, like dict[key]. See Keys and names.

##Header and query helpers

• headers.get(h, name) returns the first value of a header, or null when it is missing.
• headers.has(h, name) returns true when a header carries a value.
• headers.set(h, name, value) returns a new dict with a string or list<string> set, replacing the header regardless of name casing.
• headers.remove(h, name) returns a new dict without the header, regardless of name casing.
• headers.merge(a, b) returns a new dict with b applied over a. A null value in b removes that header.
• headers.normalize(h) returns a new dict with the names lowercased.
• query.parse(rawQuery) parses raw query text. It never guesses that its argument is a URL.
• query.fromURL(url) parses the query component of a URL.
• query.encode(query) encodes a query multimap into a query string.
• query.merge(url, query) returns the URL with the parameters applied. Null or an empty list removes a parameter.

Header and query dictionaries use cardinality-based values: dict<string, string | list<string>>. One value is a string, multiple values are a list, and zero values are an empty list. The result depends on the number of values rather than the input syntax, so a one-element input list is returned as a string. Helpers do not coerce numbers or booleans into strings. Null is not a stored value; it is accepted only as the removal marker in the patch argument to headers.merge and query.merge.

Header names are case-insensitive HTTP field names. Two forms of the same header always return an error, because picking one would depend on map order. Every header helper validates the entire input block and the requested name. Returned header names are lowercased, and headers.get returns the first value regardless of whether the stored representation is a string or list.

Query helpers keep keys and values exactly as written, including empty keys and whitespace. Encoding preserves the data but may change order and escaping. query.parse removes one leading ? as syntax and treats every other byte as query data. query.fromURL and query.merge do not trim or repair their URL argument. Use rts.text.trim explicitly when that is the behavior you want.

##Math helpers

• rts.math.abs(x) returns the absolute value.
• rts.math.min(a, b) returns the smaller value.
• rts.math.max(a, b) returns the larger value.
• rts.math.clamp(x, min, max) clamps x into the range.
• rts.math.floor(x) returns the largest integer <= x.
• rts.math.ceil(x) returns the smallest integer >= x.
• rts.math.round(x) rounds to the nearest integer (half away from zero).