Reserved Words

This page lists all reserved words and special identifiers in Weir. These cannot be used as variable or function names.

Definition Forms

Keyword	Purpose	Example
defn	Function definition	(defn add ((x : i32) (y : i32)) : i32 (+ x y))
deftype	Sum type (enum) definition	(deftype (Option 'a) (Some 'a) None)
defstruct	Product type (struct) definition	(defstruct Vec2 (x : f64) (y : f64))
defclass	Typeclass definition	(defclass (Show 'a) (show : (Fn ['a] String)))
defmacro	Macro definition	(defmacro when (cond &body body) ...)
instance	Typeclass instance	(instance (Show Vec2) (defn show ...))
declare	Separate type declaration	(declare map (Fn [(Fn ['a] 'b) (List 'a)] (List 'b)))

Expression Forms

Keyword	Purpose	Example
let	Local bindings	(let ((x 5)) (+ x 1))
if	Binary conditional	(if (> x 0) "yes" "no")
cond	Multi-branch conditional	(cond ((< x 0) "neg") (else "pos"))
match	Pattern matching	(match opt ((Some x) x) (None 0))
when	Side-effect on true	(when flag (println "yes"))
unless	Side-effect on false	(unless done (continue))
fn	Lambda / closure	(fn (x) (+ x 1))
do	Explicit sequencing	(do (step1) (step2) result)
set!	Reassign mutable binding	(set! x (+ x 1))
unsafe	Unsafe block (for FFI)	(unsafe (abs -42))
ann	Type assertion	(ann i32 42)

Modifiers

Keyword	Purpose	Example
pub	Public visibility	(pub defn spawn ...)
mut	Mutable binding	(let ((mut x 5)) (set! x 10))
else	Default branch in cond	(cond (...) (else default))

Module System

Keyword	Purpose	Example
import	Module import	(import math.vec2 (add sub))
extern	Foreign function block	(extern "C" (defn abs ...))

Operators

Symbol	Purpose
->	Thread-first macro
->>	Thread-last macro
?	Error propagation (postfix on Result)
.field	Field accessor (prefix dot)

Memory

Keyword	Purpose	Example
with-arena	Arena allocation block	(with-arena frame ...)

Built-in Types

These identifiers are reserved as type names:

Type	Description
i8, i16, i32, i64	Signed integers
u8, u16, u32, u64	Unsigned integers
f32, f64	Floating point
Bool	Boolean (true / false)
String	UTF-8 string
Unit	Unit type (one value)
Fn	Function type constructor
Vector	Vector type
Atom	Atomic reference
Channel	Typed channel
Ptr	Raw pointer (FFI)
Result	Error handling (prelude)
Ordering	Comparison result (prelude)

Built-in Values

Literal	Type	Description
true	Bool	Boolean true
false	Bool	Boolean false
None	(Option 'a)	Option empty variant
Ok	Constructor	Result success
Err	Constructor	Result error
Some	Constructor	Option present
LT	Ordering	Less than
EQ	Ordering	Equal
GT	Ordering	Greater than

Naming Conventions

Convention	Meaning	Example
kebab-case	Functions and variables	spawn-enemy, read-file
PascalCase	Types and constructors	Vec2, EnemyState, Some
:colon-prefix	Keywords (values)	:name, :health
'quote-prefix	Type variables	'a, 'elem
suffix!	Mutating operations	set!, swap!
suffix?	Predicates (return Bool)	alive?, empty?