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Catamorphism
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# Simplest Version | |
abstract type Node end | |
struct Val <: Node | |
x::Int | |
end | |
children(val::Val) = () | |
struct Add <: Node | |
a | |
b | |
end | |
children(add::Add) = (add.a, add.b) | |
interpret(val::Val) = val.x | |
interpret(add::Add) = add.a + add.b | |
cata_(f, node::T, children) where T = f(T(map(x_ -> cata(f, x_), children)...)) | |
cata_(f, node, children::Tuple{}) = f(node) | |
cata(f, node) = cata_(f, node, children(node)) | |
term = Add(Add(Val(1), Val(2)), Val(3)) | |
cata(interpret, term) | |
swap(add::Add) = Add(add.b, add.a) | |
swap(v::Val) = v | |
cata(swap, term) |
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I misread the code. I deleted that comment before I saw your reply.