RDL Macros

The final type of macro that we are going to look at is one that allows you to create custom NDL patterns. These are called NDL macros and work like this:

Syntax

A NDL macro can be created in Ryna using this syntax:

syntax rdl macro_name from NDL_Pattern {
    [...]
}

This macro would have to create a string that can be parsed as an NDL pattern. This syntax can then be used safely inside any implicit class syntax or macro.

This would be an example that transforms a pattern into a series of that pattern separated by commas (again, note that we need to escape the closing brace):

syntax rdl comma_separated from "#" s Arg(<rdl>, inner) s "#" {
    $inner { ", " $inner \}
}

// Usage example
class Ints {
    // This pattern es equivalent to "[" Arg(1{d}, ints) {", " Arg(1{d}, ints)} "]"
    syntax from "[" # Arg(1{d}, ints) # "]";

    ints: Array<Int>;
}

let a: Ints = [1, 2, 3];