HHY Reference

Complete Syntax Reference

V1.0 lexical rules, literals, operators, statements, closures, and module syntax.

Source files and lexical rules

Item	Rule
File	.hhy, UTF-8, LF or CRLF
Identifier	Case-sensitive ASCII letters, digits, and underscores; cannot start with a digit
Statement end	Newline or optional semicolon
Continuation	Open delimiters or leading/trailing \|>
Comment	# line comment; first line may be a shebang
/	Regex at expression start, division after a left operand

Literals and native units

let nothing = null
let flags = [true, false]
let numbers = [42, -10, 0xff, 0b1010, 1.5, 1e6]
let name = "HHY"
let strings = ["hello", "Hello, {name}"]
let pattern = /ERROR|WARN/i
let list = [1, 2, 3]
let record = { name: "Tom", age: 20 }
let interval = 1..10
let units = [10mib, 5s, 80%]

Ranges include the start and exclude the end. Bytes support b/kb/mb/gb/kib/mib/gib; Duration supports ns/us/ms/s/min/h; % attached to a number creates Percent. Strings support interpolation and \, ", \n, \r, \t, \b, \f, and \0 escapes.

Operator precedence (highest to lowest)

()  []  .
not  -  +
*  /  %
+  -
<  <=  >  >=
==  !=
and
or
??
|>
=

and, or, and ?? short-circuit; = may assign only to a let mut binding; |> is left-associative. Conditions require Bool—0, empty strings, and null are not implicitly false.

Declarations, control flow, functions, and modules

let name = "HHY"
let mut count = 0
count = count + 1
let enabled = true
let items = ["Flow", "Pipe"]

if enabled { print("yes") } else { print("no") }
for item in items { print(item) }
while count < 3 { count = count + 1 }

fn add(a, b) { return a + b }
let doubled = [1, 2] |> stream |> map { number -> number * 2 } |> collect

try { read_text(path("config.json")) } catch err { print_error(err) }
let result = attempt { read_text(path("config.json")) }

import { add as sum_two } from "./math.hhy"
export fn public_api(value) { return value }

Construct	Form
Call	name(args)
Pipe	x \|> f(a) equals f(x, a)
Closure	{ param -> expression }
Map	{ key: value }
Control flow	if, for, while, break, continue, return
Module	import, as, export

Core value types

Null Bool Int Float String Regex BytesBuffer
List Map Range Function Error Result Stream
Bytes Duration Percent DateTime Path
File Directory FileEvent Process CommandResult
HttpRequest HttpResponse