Primitive Types

This chapter covers Compact’s primitive types - the building blocks for all data in your contracts.

Overview

Compact provides several primitive types:

Type	Description	Example
`Boolean`	True/false values	`true`, `false`
`Field`	Elements of the proving system’s scalar field	Used in ZK proof arithmetic
`Uint<n>`	Sized unsigned integers (up to `n` bits, max width 248)	`Uint<64>`, `Uint<128>`
`Uint<0..n>`	Bounded unsigned integers from `0` up to (not including) `n`	`Uint<0..101>` for percentages 0-100
`Bytes<n>`	Fixed-length byte arrays	`Bytes<32>` for hashes or identifiers
`Opaque<s>`	Opaque values tagged by a string literal (`"string"`, `"Uint8Array"`)	`Opaque<"string">`

Note: Uint<n> and Uint<0..n> are the same type family. Uint<n> is exactly equivalent to Uint<0..2^n> (exclusive upper bound).

Each type serves a specific purpose in zero-knowledge circuits. Let’s explore them in detail.