CODEWITHSUNDEEP
luavariadic-functions
rtxndr
rtxndr

Reputation: 932

What does this function return

function f(...)
  return ...
end

And I call it like this:

f()

Example

a = f()
print(a) -- echoes 'nil', same as print(nil)

But

print(f()) -- echoes newline, same as print(), that is, no args
t = {f()} -- same as t = {}

So, what does f() return?

Update: did not know that functions can return 'void', found this http://lua-users.org/lists/lua-l/2011-09/msg00289.html meanwhile.

Upvotes: 2

Views: 2852

Answers (3)

ROMANIA_engineer
ROMANIA_engineer

Reputation: 56714

The answer regarding the type could be the output of this command:

print(type(f()))

In this case, it prints:

bad argument #1 to 'type' (value expected)

So, a value is expected, but there is no value. => It returns nothing (void).

So, it's a normal behaviour to have: t = {f()} <=> t = {}

Regarding the assignment, Lua assigns by default the nil value if there is no value.

Upvotes: 3

rtxndr
rtxndr

Reputation: 932

I found that Lua function can return 'nothing', not even a nil. In this case, f() returns nothing. Using nothing (without assignment) results in zero arguments in another function call(like print(f()) or in table constructor({f()}).

print(a) echoed nil because a had no assigned value, print(any_name) will echo nil aswell.

Upvotes: 2

mabako
mabako

Reputation: 1183

It returns all parameters you called it with.

f() -- has no parameter, returns nothing

If you do an assignment with less values than you have variables, i.e.

local a, b = 3
local c

Then that'll just end up with b and c being nil.

On the other hand, this would all do something:

f(1) -- returns 1
f(1, 2, 3) -- returns 1, 2 and 3
local t = {f(1, 2, 3)} -- table with the values 1, 2 and 3

Upvotes: 5

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