Functions in Noir follow the same semantics of Rust, Noir does not support early returns.

To declare a function the fn keyword is used.

fn foo() {}

All parameters in a function must have a type and all types are known at compile time. The parameter is pre-pended with a colon and the parameter type. Multiple parameters are separated using a comma.

fn foo(x : Field, y : pub Field){}

The return type of a function can be stated by using the -> arrow notation. The function below states that the foo function must return a Witness. If the function returns no value, then the arrow is omitted.

fn foo(x : Field, y : pub Field) -> Field {
    x + y

Call Expressions

Calling a function in Rust is executed by using the function name and passing the necessary arguments the function header.

Below we show how to call the foo function from the main function using a call expression:

fn main(x : Field, y : Field) {
    priv z = foo(x);

fn foo(x : Field) -> Field {
    x + x