lua - strange behavior of table.unpack - Stack Overflow

Suppose I have two Lua arrays a = {1, 2, 3} and b = {4, 5, 6}.

And then do the following assignation

q, w, e, r, t, y = table.unpack(a), table.unpack(b)

I would expect to get that

q == 1 and w == 2 and e == 3 and r == 4 and t == 5 and y == 6

But I get that q == 1 and w == 4 and e == 5 and r == 6 and t, y are nil!

Could you please explain such a strange behavior?

Suppose I have two Lua arrays a = {1, 2, 3} and b = {4, 5, 6}.

And then do the following assignation

q, w, e, r, t, y = table.unpack(a), table.unpack(b)

I would expect to get that

q == 1 and w == 2 and e == 3 and r == 4 and t == 5 and y == 6

But I get that q == 1 and w == 4 and e == 5 and r == 6 and t, y are nil!

Could you please explain such a strange behavior?

• lua

Share Improve this question Follow asked Jan 2 at 20:22 OlegOleg 1955 bronze badges

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1 Answer 1

Sorted by: Reset to default 5

From the Lua documentation on multiple results:

Lua always adjusts the number of results from a function to the circumstances of the call. When we call a function as a statement, Lua discards all of its results. When we use a call as an expression, Lua keeps only the first result. We get all results only when the call is the last (or the only) expression in a list of expressions.

So table.unpack(a), table.unpack(b) doesn't concatenate all return values from both calls. You get the first return value of table.unpack(a), followed by all return values of table.unpack(b).