Skip to main content

Generics

Swirl supports generics, which are monomorphized into concrete constructs by the compiler.

Genric functions​

Example:

fn generic<T>(a: T) {  
    ...
}

fn main() {
    generic!<i32>(43);
}

Generic structs​

Example:

struct Generic<T> {
    var member: T;
}

fn main() {
    var member: Generic<i32>;
}

The !<...> arg list syntax is only required in expression context to disambiguate generic arg lists from expressions (where they conflict with the < and > operator), in type-context, the ! can be omitted as shown above.

Comptime values as generic args​

Swirl allows you to pass comptime expressions as generic arguments, to do so, simply precede the comptime expression with the comptime keyword as shown below.

fn return_number<N>() { return N; }

fn main() {
   return return_number!<comptime 8>();
}

Generic Constraints​

Generics parameters can be constrained by one or multiple protocols:

fn one_protocol_constraint<T: P>() {
    ...
}


fn multiple_protocol_constraints<T: [P, Q, R]> {
    ...
}

where P, Q and R are protocols. The compiler enforces the argument of T in both cases to implement all the prescribed protocols.

Stay informed​