Possible to match a NamedTuple?

[fredcallaway]

I didn't see this in the docs so I assume it's not possible. It would be really nice to be able to match NamedTuples, e.g.

@match (;a=1, b=2) begin
    (;a=1, b) => begin
        # I would like to have locals a = 1 and b = 2
    end
end

[xukai92]

had a similar need and found the following work-around works

nt = (; a=1, b=2)
NT = typeof(nt)
@match (; a, b) = nt begin
    NT(1, b) => begin
        # you have access to locals a = 1 and b = 2 here
    end
end

[fredcallaway]

@xukai92 It looks like this only works for a single type of named tuple. Could be handy, but definitely not a complete solution.

[xukai92]

yeah but NT is constructed programmatically so I guess it's good enough as a work-around.
i guess this logic can be potentially implemented within @match so to achieve the behavior similar to your OP

[fredcallaway]

I had that thought as well, but I'm not sure how you would handle a case where you want to match on a named tuple that could have different types, e.g.

nt = rand((
    (;a=1, b=2),
    (x = "x", y="z")
))
@match nt begin
    (;a=1, b) => begin
        @show a b
    end
    (;x, y) => begin
        @show x y
    end
end

[xukai92]

i guess in that case you will have to do something even more messy (deconstructing in the match statements)

nts = (
    (; a=1, b=2),
    (; x="x", y="z"),
)
NT1, NT2 = typeof.(nts)

nt = rand(nts)
@match nt begin
    NT1(1, b) => begin
        (; a, b) = nt
        @show a b
    end
    NT2(x, y) => begin
        (; x, y) = nt
        @show x y
    end
end