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zelphirkalt • last Friday at 2:02 AM • 1 reply • view on HN

Instead of defining a Visitor interface and then making objects to implement the interface and then passing those objects to whatever traverses a graph or iterates through something, you pass the function, that will be called, by whatever traverses a graph or iterates through something.

Replies

vips7L • last Friday at 5:13 PM

Kind of like how sum types and matching are implemented in library code? Example from D here:

    Fahrenheit toFahrenheit(Temperature t)
    {
        return Fahrenheit(
            t.match!(
                (Fahrenheit f) => f.degrees,
                (Celsius c) => c.degrees * 9.0/5 + 32,
                (Kelvin k) => k.degrees * 9.0/5 - 459.4
            )
        );
    }