CODEWITHSUNDEEP
luamultiple-assignment
wimalopaan
wimalopaan

Reputation: 5472

LUA: howto omit a value of a multi-value in a multiple-assignment

If I want only the first and the third value of the function f(), I can do the following:

local a, _, b = f();

Since _ is a valid name, maybe _ gets assigned a large table.

Is there a way to omit this assignent to _ in the above case? (Clearly: if _ goes out of scope it is gc'ed).

Upvotes: 3

Views: 115

Answers (2)

Piglet
Piglet

Reputation: 28994

Is there a way to omit this assignent to _ in the above case?

No there is no way to omit that assignment if you need the third return value. You can only make sure not to keep the returned object alive by referring to it through _. Of course this only makes a difference if there is no other reference left.

In addition to using a function to limit _'s scope you can also use do end

local a,c
do
  local _ a,_,c = f()
end

or you simply remove the unused reference.

local a, _, c = f()
_ = nil

Upvotes: 3

Ivo
Ivo

Reputation: 23357

Not sure if it helps but maybe you can define a helper function like

function firstAndThird(a, b, c)
    return a, c
end

and then use it like

local a, b = firstAndThird(f());

Upvotes: 4

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