Integers

An integer type is a range constrained field type. The Noir frontend currently supports unsigned, arbitrary-sized integer types.

Note: When an integer is defined in Noir without a specific type, it will default to Field. The one exception is for loop indices which default to u64 since comparisons on Fields are not possible.

An integer type is specified first with the letter u, indicating its unsigned nature, followed by its length in bits (e.g. 32). For example, a u32 variable can store a value in the range of $\\([0,2^{32}-1]\\)$.

Note: The default proving backend supports both even (e.g. u16, u48) and odd (e.g. u5, u3) sized integer types.

Taking a look of how the type is used:

fn main(x : Field, y : u32) {
    let z = x as u32 + y;
}

x, y and z are all private values in this example. However, x is a field while y and z are unsigned 32-bit integers. If y or z exceeds the range $\\([0,2^{32}-1]\\)$, proofs created will be rejected by the verifier.