unpack function issue in Lua

Question

I have the following unpack() function:

function unpack(t, i)  
    i = i or 1  
    if t[i] then  
        return t[i], unpack(t, i + 1)  
    end  
end  

I now use it in the following test code:

t = {"one", "two", "three"}  
print (unpack(t))  
print (type(unpack(t)))  
print (string.find(unpack(t), "one"))  
print (string.find(unpack(t), "two"))

which outputs:

one two three  
string  
1   3  
nil  

What puzzles me is the last line, why is the result nil?

Answer 1

If a function returns multiple values, unless it's used as the last parameter, only the first value is taken.

In your example, string.find(unpack(t), "one") and string.find(unpack(t), "two"), "two" and "three" are thrown away, they are equivalent to:

string.find("one", "one")  --3

and

string.find("one", "two")  --nil