julia> bar(a,b,x...) = (a,b,x) bar (generic function with 1 method) julia> bar(1,2) (1,2,()) Is () a zero-argument anonymous function that takes in varargs, making zero really mean any-argument anonymous function? If yes, then to me, the name zero-argument name just doesn’t fully capture/represent…

() is just parenthesis. In general it’s used when the syntax can otherwise be ambiguous. In most cases it’s optional. You can write x->x instead of (x)->x, x, y instead of (x, y). Zero element tuples and zero argument functions needs the () since it’ll be hard to represent otherwise. And [imag…

[image] hpoit: () a zero-argument anonymous function No, it’s an empty tuple.

So can () take var-args? Below, can ()->3 also take varargs? julia> o = ()->3 # ()->3 officially named as zero-argument (::#1) (generic function with 1 method) julia> o() 3 Is () an empty tuple that takes var-args?

The () in ()->3 is not a name. It is also akin to an empty tuple. Tuples represent the arguments of functions; an empty tuple means that the function takes no arguments. f() = 3 and const f = ()->3 are basically defining the same thing.

[image] mbauman: an empty tuple means that the function takes no arguments. So (1,2,()) means bar won’t take any other args other than 1,2, that’s all it means? julia> bar(a,b,x...) = (a,b,x) bar (generic function with 1 method) julia> bar(1,2) (1,2,())

[image] hpoit: So (1,2,()) means bar won’t take any other args other than 1,2, that’s all it means? No it means you didn’t give it “any other args other than 1, 2”

Okay, so it states the obvious, could’ve been bar(1,2) => (1,2)?

Try bar(1, 2, 3) and bar(1, 2, 3, 4, 5) to understand what the splat (...) does.

[image] hpoit: Okay, so it states the obvious, could’ve been bar(1,2) # => (1,2)? No. for bar(1, 2) x = (). Please read the full section of https://docs.julialang.org/en/latest/manual/functions.html#Varargs-Functions-1

Yup, that exact Doc section led me here. Your previous comment about representing a zero element tuple drove the point home. It must be represented, even though there’s nothing you can do with it. Thanks.

julia> x = () () julia> typeof(x) Tuple{} julia> length(x) 0

The zero-argument anonymous function name

General Usage

yuyichao May 31, 2017, 11:05pm 2

No, it’s an empty tuple.

Topic		Replies	Views
Why does defining a vararg method define a zero argument method? Internals & Design question	32	1945	February 4, 2021
Argument destructuring and anonymous functions General Usage	8	3137	June 4, 2019
Trouble in understanding how to use varargs as a constructor New to Julia	7	1084	August 30, 2018
Speeding Up Function with ::Function and ::Vararg input Performance	17	1053	February 19, 2021
Function arguments General Usage tuple , function , namedtuple , named-tuple	37	2039	December 20, 2024

The zero-argument anonymous function name

Related topics