Aver

All functions live in namespaces — no flat builtins (decision: FullNamespaceEverywhere).

Pure namespaces (no effects)

Bool namespace

Source: src/types/bool.rs

Function	Signature	Notes
Bool.or	(Bool, Bool) -> Bool	Logical OR
Bool.and	(Bool, Bool) -> Bool	Logical AND
Bool.not	Bool -> Bool	Logical NOT

List namespace

Source: src/types/list.rs

List is a recursive structure — use it for sequential processing with prepend, take, drop, and match [h, ..t]. For indexed access, use Vector.

Function	Signature	Notes
List.len	List<T> -> Int
List.prepend	(T, List<T>) -> List<T>	O(1) prepend
List.take	(List<T>, Int) -> List<T>	First n elements; negative n yields []
List.drop	(List<T>, Int) -> List<T>	All but first n elements; negative n keeps the original list
List.concat	(List<T>, List<T>) -> List<T>	Concatenates two lists
List.reverse	List<T> -> List<T>	Returns a reversed copy
List.contains	(List<T>, T) -> Bool	Membership check via ==
List.zip	(List<A>, List<B>) -> List<(A, B)>	Pairs elements, truncates to shorter list

Vector namespace

Source: src/types/vector.rs

Vector is a persistent indexed sequence — use it for grids, buffers, lookup tables, and anywhere you need O(1) access by index. Backed by Rc<Vec<T>> with copy-on-write: set mutates in place when the vector has a single owner, clones otherwise.

Function	Signature	Notes
Vector.new	(Int, T) -> Vector<T>	Create vector of N elements, all set to default
Vector.get	(Vector<T>, Int) -> Option<T>	O(1) indexed access
Vector.set	(Vector<T>, Int, T) -> Option<Vector<T>>	O(1) COW update; None if out of bounds
Vector.len	Vector<T> -> Int
Vector.fromList	List<T> -> Vector<T>	Convert list to vector
List.fromVector	Vector<T> -> List<T>	Convert vector to list

Result namespace

Source: src/types/result.rs + constructors in src/vm/runtime.rs.

Function	Signature	Notes
Result.Ok	T -> Result<T, E>	Constructor
Result.Err	E -> Result<T, E>	Constructor
Result.withDefault	(Result<T, E>, T) -> T	Unwrap Ok or return default

Option namespace

Source: src/types/option.rs + constructors in src/vm/runtime.rs.

Function	Signature	Notes
Option.Some	T -> Option<T>	Constructor
Option.None	Option<T>	Value (not a function)
Option.withDefault	(Option<T>, T) -> T	Unwrap Some or return default
Option.toResult	(Option<T>, E) -> Result<T, E>	Convert Option to Result

Int namespace

Source: src/types/int.rs

Function	Signature
Int.fromString	String -> Result<Int, String>
Int.fromFloat	Float -> Int
String.fromInt	Int -> String
Float.fromInt	Int -> Float
Int.abs	Int -> Int
Int.min	(Int, Int) -> Int
Int.max	(Int, Int) -> Int
Int.mod	(Int, Int) -> Result<Int, String>

Float namespace

Source: src/types/float.rs

Function	Signature
Float.fromString	String -> Result<Float, String>
Float.fromInt	Int -> Float
String.fromFloat	Float -> String
Float.abs	Float -> Float
Float.floor	Float -> Int
Float.ceil	Float -> Int
Float.round	Float -> Int
Float.min	(Float, Float) -> Float
Float.max	(Float, Float) -> Float
Float.sin	Float -> Float
Float.cos	Float -> Float
Float.sqrt	Float -> Float
Float.pow	(Float, Float) -> Float
Float.atan2	(Float, Float) -> Float
Float.pi	() -> Float

String namespace

Source: src/types/string.rs

Function	Signature	Notes
String.len	String -> Int	Number of characters (Unicode scalar values), on every backend
String.byteLength	String -> Int	UTF-8 byte count
String.charAt	(String, Int) -> Option<String>	Character at character index, or Option.None on out-of-bounds
String.startsWith	(String, String) -> Bool
String.endsWith	(String, String) -> Bool
String.contains	(String, String) -> Bool
String.slice	(String, Int, Int) -> String	Character indices; out-of-range ends clamp
String.trim	String -> String
String.split	(String, String) -> List<String>
String.replace	(String, String, String) -> String
String.join	(List<String>, String) -> String
String.chars	String -> List<String>	Splits into characters (Unicode scalar values)
String.fromInt	Int -> String
String.fromFloat	Float -> String
String.fromBool	Bool -> String
String.toLower	String -> String	Unicode-aware lowercase
String.toUpper	String -> String	Unicode-aware uppercase

Map namespace

Source: src/types/map.rs

Function	Signature	Notes
{} (literal)	—	The empty map; type from context (annotation or expected type). No Map.empty() builtin since 0.17 — symmetric with [] for List.
Map.fromList	List<(K, V)> -> Map<K, V>	Keys must be hashable (Int, Float, String, Bool)
Map.set	(Map<K, V>, K, V) -> Map<K, V>	Returns new map with key set
Map.get	(Map<K, V>, K) -> Option<V>
Map.has	(Map<K, V>, K) -> Bool
Map.remove	(Map<K, V>, K) -> Map<K, V>	Returns new map without key
Map.keys	Map<K, V> -> List<K>
Map.values	Map<K, V> -> List<V>
Map.entries	Map<K, V> -> List<(K, V)>
Map.len	Map<K, V> -> Int

Sets: Map<T, Unit> is the Aver way to have a set — see language.md for usage and codegen lowering.

Char namespace

Source: src/types/char.rs — not a type, operates on String/Int.

Function	Signature	Notes
Char.toCode	String -> Int	Unicode scalar value of first char
Char.fromCode	Int -> Option<String>	Code point to 1-char string, Option.None for surrogates/invalid

Byte namespace

Source: src/types/byte.rs — not a type, operates on Int/String.

Function	Signature	Notes
Byte.toHex	Int -> Result<String, String>	Always 2-char lowercase hex
Byte.fromHex	String -> Result<Int, String>	Exactly 2 hex chars required

Effectful namespaces

Namespace effect shorthand: declaring ! [ServiceName] covers all methods of that service. For example, ! [Disk] is equivalent to ! [Disk.readText, Disk.writeText, Disk.appendText, Disk.exists, Disk.delete, Disk.deleteDir, Disk.listDir, Disk.makeDir]. You can still use granular declarations like ! [Disk.readText] when you want to be precise. aver check suggests narrowing when a shorthand could be more specific.

Args namespace — use ! [Args.get]

Source: src/services/args.rs

Function	Signature	Notes
Args.get	() -> List<String>	Command-line arguments passed after --

Usage: aver run file.av -- arg1 arg2 arg3

fn main() -> Unit
    ! [Args.get, Console.print]
    args = Args.get()
    Console.print(args)

Console namespace — use ! [Console.print], ! [Console.error], etc.

Source: src/services/console.rs

Function	Signature
Console.print	T -> Unit
Console.error	T -> Unit (writes to stderr)
Console.warn	T -> Unit (writes to stderr)
Console.readLine	() -> Result<String, String>

Http namespace — use granular effects (! [Http.get], ! [Http.post], etc.)

Source: src/services/http.rs

Function	Signature	Notes
Http.get	String -> Result<HttpResponse, String>
Http.head	String -> Result<HttpResponse, String>
Http.delete	String -> Result<HttpResponse, String>
Http.post	(String, String, String, Map<String, List<String>>) -> Result<HttpResponse, String>	url, body, content-type, headers
Http.put	(String, String, String, Map<String, List<String>>) -> Result<HttpResponse, String>
Http.patch	(String, String, String, Map<String, List<String>>) -> Result<HttpResponse, String>

HttpResponse record: { status: Int, body: String, headers: Map<String, List<String>> }. Headers are a multimap — a single name can carry multiple values (Set-Cookie, Vary, …).

HttpServer namespace — use ! [HttpServer.listen] or ! [HttpServer.listenWith]

Source: src/services/http_server.rs

Function	Signature
HttpServer.listen	(Int, Fn(HttpRequest) -> HttpResponse ! [...method-level effects...]) -> Unit
HttpServer.listenWith	(Int, T, Fn(T, HttpRequest) -> HttpResponse ! [...method-level effects...]) -> Unit

HttpServer.listen and HttpServer.listenWith accept top-level function values. listenWith is the preferred form when a handler needs configuration, connections, or other app state, because the context stays explicit instead of being hidden in closure capture.

This is the main intended use of function values in Aver: named handlers and callbacks with explicit types and explicit effects. Most user code still stays first-order.

The handler itself still uses exact method-level effects such as Http.get, Tcp.readLine, or Console.print. The server call does not widen those into namespace-level grants.

HttpRequest record: { method: String, path: String, body: String, headers: Map<String, List<String>> }. HttpResponse record: { status: Int, body: String, headers: Map<String, List<String>> }. Header keys are case-insensitive by convention (the runtime normalises incoming names to lowercase; outgoing should match).

The caller declares only HttpServer.listen / HttpServer.listenWith. The handler carries its own ! [...] declaration; its effects are checked on the handler function itself rather than copied onto the caller.

Disk namespace — use granular effects (! [Disk.readText], ! [Disk.writeText], etc.)

Source: src/services/disk.rs

Function	Signature	Notes
Disk.readText	String -> Result<String, String>
Disk.writeText	(String, String) -> Result<Unit, String>	path, content
Disk.appendText	(String, String) -> Result<Unit, String>
Disk.exists	String -> Bool
Disk.delete	String -> Result<Unit, String>	Files only
Disk.deleteDir	String -> Result<Unit, String>	Recursive
Disk.listDir	String -> Result<List<String>, String>
Disk.makeDir	String -> Result<Unit, String>	Creates parents

Tcp namespace — use granular effects (! [Tcp.send], ! [Tcp.ping], etc.)

Source: src/services/tcp.rs

One-shot (stateless):

Function	Signature
Tcp.send	(String, Int, String) -> Result<String, String>
Tcp.ping	(String, Int) -> Result<Unit, String>

Persistent connections:

Function	Signature	Notes
Tcp.connect	(String, Int) -> Result<Tcp.Connection, String>	Opaque handle — see below.
Tcp.writeLine	(Tcp.Connection, String) -> Result<Unit, String>	Appends \r\n on the wire.
Tcp.readLine	Tcp.Connection -> Result<String, String>	Strips the trailing \r\n; Ok("") on a clean EOF before any byte.
Tcp.close	Tcp.Connection -> Result<Unit, String>	Err("tcp: unknown connection ...") on a double-close.

Tcp.Connection is opaque from the surface: construction is reserved to Tcp.connect and field reads / pattern matches are rejected by the type checker. The handle is purely an identity token — the caller has nothing to inspect inside it. The underlying socket lives in a thread-local HashMap (VM / self-host / wasm-gc-bridge, keyed by AtomicU64 "tcp-N") or a 256-slot wasm-gc array (--target wasip2, slot allocated via first-free scan + monotonic counter generation). Either way, manually forging an id is impossible: the type checker rejects the constructor.

Tcp.send is stateless and ephemeral — it opens a fresh socket, writes the request bytes raw (no \r\n append), shutdown(Write) to signal end-of-request, then reads the peer's response until EOF, capped at 10 MiB. It does not touch the persistent-connection pool, so a program holding 256 live Tcp.connect handles can still issue Tcp.send to another peer. Stream errors (stream-error.last-operation-failed) surface as Result.Err("tcp: stream error"); a clean half-close (stream-error.closed) returns whatever the peer flushed.

Random namespace — use granular effects (! [Random.int], ! [Random.float])

Source: src/services/random.rs (backed by aver_rt::random)

Function	Signature	Notes
Random.int	(Int, Int) -> Int	Random integer in [min, max] inclusive
Random.float	() -> Float	Random float in [0.0, 1.0)

Time namespace — use granular effects (! [Time.now], ! [Time.unixMs], ! [Time.sleep])

Source: src/services/time.rs

Function	Signature	Notes
Time.now	() -> String	Current UTC timestamp string (...Z)
Time.unixMs	() -> Int	Unix epoch milliseconds
Time.sleep	Int -> Unit	Sleeps current thread for ms, runtime error on negative

Terminal namespace — use granular effects (! [Terminal.clear], ! [Terminal.readKey], etc.)

Source: src/services/terminal.rs (requires terminal feature, enabled by default)

Function	Signature	Notes
Terminal.enableRawMode	() -> Unit	Enter raw mode (no line buffering, no echo)
Terminal.disableRawMode	() -> Unit	Leave raw mode
Terminal.clear	() -> Unit	Clear entire screen
Terminal.moveTo	(Int, Int) -> Unit	Move cursor to column x, row y
Terminal.print	a -> Unit	Print at cursor position (no newline)
Terminal.setColor	String -> Unit	Set foreground: "red"/"green"/"yellow"/"blue"/"white"/"cyan"/"magenta"/"black"
Terminal.resetColor	() -> Unit	Reset colors to default
Terminal.readKey	() -> Option<String>	Non-blocking poll: "up"/"down"/"left"/"right"/"esc"/"q"/char or None
Terminal.size	() -> Terminal.Size	Returns Terminal.Size { width: Int, height: Int }
Terminal.hideCursor	() -> Unit	Hide cursor
Terminal.showCursor	() -> Unit	Show cursor
Terminal.flush	() -> Unit	Flush stdout

Terminal guard: aver run installs a drop guard that restores the terminal (show cursor, reset colors, disable raw mode) even on panic or runtime error.

Env namespace — use granular effects (! [Env.get], ! [Env.set])

Source: src/services/env.rs

Function	Signature	Notes
Env.get	String -> Option<String>	Returns Option.None for missing/unreadable variable
Env.set	(String, String) -> Unit	Runtime error on invalid key/value format

Runtime policy (aver.toml) can restrict allowed keys:

[effects.Env]
keys = ["APP_*", "PUBLIC_*"]