Types

BitterASM has exactly one built-in type, int. Every other type is declared in BitterASM code, usually in a library:

Kind	Declared with	Example
Struct	`struct`	an instruction format, `bits<N>`, `Array<T, N>`
Enum	`enum`	`Endian { Little, Big }`, `Option<T>`
Type alias	`type`	`type Reg = bits<5>`

Types can be generic: bits<8> and Array<int, 4> are instances of generic structs.

Why types matter

Types exist only at compile time. The compiler uses them to:

Check arguments. A macro that takes a Reg rejects anything that isn’t a Reg.
Pick overloads. mov rax, rbx and mov rax, 5 call different mov macros because rbx and 5 have different types. See Overloading.
Enforce rules. An invariant such as “fits in 8 bits” or “is even” is checked every time a value of the type is made.
Describe output. A struct’s fields tell an evaluator like bitter how to lay out bits. See Packing bytes with bitter.

A value never changes type on its own. To turn one type into another, convert it explicitly with as:

from std.binary import bits

macro emit_byte(b: bits<8>) {
    @emit b
}

emit_byte 65 as bits<8>

bits<8> { value: 65 }

== and != work on any two values: structs compare field by field, and enums compare variant and payload.