function at line xxx has more than 60 upvalues - lua

Question

I have written some lua code like this:
local a1 = 1
local a2 = 2
local a3 = 3
local a4 = 3
local a5 = 3
local a6 = 3
local a7 = 3
local a8 = 3
local a9 = 3
local a10 = 3
local a11 = 3
local a12 = 3
local a13 = 3
local a14 = 3
local a15 = 3
local a16 = 3
local a17 = 3
local a18 = 3
local a19 = 3
local a20 = 3
local a21 = 3
local a22 = 3
local a23 = 3
local a24 = 3
local a25 = 3
local a26 = 3
local a27 = 3
local a28 = 3
local a29 = 3
local a30 = 3
local a31 = 1
local a32 = 2
local a33 = 3
local a34 = 3
local a35 = 3
local a36 = 3
local a37 = 3
local a38 = 3
local a39 = 3
local a40 = 3
local a41 = 3
local a42 = 3
local a43 = 3
local a44 = 3
local a45 = 3
local a46 = 3
local a47 = 3
local a48 = 3
local a49 = 3
local a50 = 3
local a61 = 3
local a62 = 3
local a63 = 3
local a64 = 3
local a65 = 3
local a66 = 3
local a67 = 3
local a68 = 3
local a69 = 3
local a70 = 3
local function fun1(x1, x2, x3, x4, x5, x6, x7, x8, x9, x10)
print('.......')
end
local function fun2()
fun1(a1, a2, a3, a4, a5, a6, a7, a8, a9, a10)
fun1(a11, a12, a13, a14, a15, a16, a17, a18, a19, a20)
fun1(a21, a22, a23, a24, a25, a26, a27, a28, a29, a30)
fun1(a31, a32, a33, a34, a35, a36, a37, a38, a39, a40)
fun1(a41, a42, a43, a44, a45, a46, a47, a48, a49, a50)
fun1(a51, a52, a53, a54, a55, a56, a57, a58, a59, a60)
fun1(a61, a62, a63, a64, a65, a66, a67, a68, a69, a70)
end
and i got an error like this when ran this code:
78: function at line 71 has more than 60 upvalues
i know this kind of code is ugly and i can use some way else to do it (like table), but this kind of code may be written by my users.
can someone explain this for me, and tell me how to avoid this? thanks very much.

Answer 1

tell me how to avoid this?
There's the old joke. A guy walks into a doctor's office and says, "It hurts when I raise my arm like this." The doctor says, "So don't raise your arm like that."
If your users write Lua code that does not compile, that's not something you can fix. This is no more illegitimate a compile error than something like:
if condition --forgot the then
return something
end
So if your code is going to accept arbitrary Lua scripts to compile and execute, it will need to be able to deal with Lua scripts that don't compile. For whatever reason.
If compilation fails, report the error to the user and recover the best you can.

Answer 2

Maximum 60 upvalues, that is values from outer scopes that your closure is closed over, is one of internal Lua limits. Of course you can change it by recompiling Lua itself, but I'd advise against it. Pack your values in some table instead, with its layout dictated by logic of code. In your particular example you really should be using:
local a = {}
a[1] = 1
a[2] = 2
a[3] = 3
a[4] = 3
a[5] = 3
-- etc...