When working with tuples, you can ‘pop’ the first entry via dispatch as follows:

```
tuplepop(t::Tuple{<:Any, Vararg}) = t[2:end]
tuplepop(t::Tuple{}) = t
```

But how can I determine the type of the result ahead of time?

This is the best I can come up with, but it’s hideous:

```
tuplepop_type(::Type{T}) where T<:Tuple{<:Any, Vararg} = Tuple{T.parameters[2:end]...}
tuplepop_type(::Type{Tuple{}}) = Tuple{}
```

I’d just use `tuplepop(t::Tuple) = typeof(Base.tail(t))`

That’ll error on empty tuples, but you can easily add the `Tuple{}`

case as a second method.

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Thank you, easy solution!

Oh wait, actually is there some way of determining the return type with only the argument type? It’d be nice to just work with the types.

```
julia> Base.tuple_type_tail(Tuple{Int,Int,Float64})
Tuple{Int64,Float64}
```

It’s not exported, but it’s better than all other non-exported methods for doing the same.

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Thanks! There’s an amazing amount of useful things lurking in Base.

Do you know what Julia’s policy is on non-exported functions in Base? I assume if functions are not exported from Base then there’s no guarantee that they won’t disappear across versions.

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They can indeed disappear without deprecations, but at least the maintainers of `Base`

do not to introduce different semantics and keep the name, so your unit tests should catch the change and you can rewrite.

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