Slurping on non-final argument

Internals & Design Internals
1

why can i define this function?

julia> f(y,x...)=+(x...).*y
f (generic function with 1 method)

and can’t I define this other one?

julia> f1(x...,y)=+(x...).*y
ERROR: syntax: invalid "..." on non-final

Couldn’t we gnisrap the arguments in reverse order?

I guess there are many possible side effects to avoid but I am not able to imagine.

2

See this thread: Optional positional arguments must occur at end - #13 by Jean_Michel

3

This seems to be about slurping, not about optional arguments.

Here’s a PR that addresses this: https://github.com/JuliaLang/julia/pull/42902
Not sure when/if it will land.

But currently, this is not allowed.

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4

Note that the PR doesn’t address method dispatch as the OP asked for. That would require changes to the type system to actually be able to represent signatures like this.

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