-- Tables and functions compare by identity.
local t = {}
local u = {}
assert(t == t, "a table should equal itself")
assert(t != u, "distinct tables should not be equal")
local f = function() end
assert(f == f, "a function should equal itself")
assert(f != function() end, "distinct functions should not be equal")
assert(print == print, "a native function should equal itself")
-- Multiple assignment evaluates the right side before assigning.
local a, b = 1, 2
a, b = b, a
assert(a == 2 and b == 1, "swap should exchange values")
local function triple() return 10, 20, 30 end
local x, y, z, w = 0, 0, 0, "keep"
x, y, z = triple()
assert(x == 10 and y == 20 and z == 30, "call results should spread across targets")
assert(w == "keep", "untouched targets should keep their values")
local obj = { n = 1 }
obj.n, obj.m = 5, 6
assert(obj.n == 5 and obj.m == 6, "member targets should be assignable together")
local short, missing = 0, 0
short, missing = 1
assert(short == 1 and missing == nil, "missing values should become nil")
-- Compound assignment.
local n = 10
n += 5
assert(n == 15, "+=")
n -= 3
assert(n == 12, "-=")
n *= 2
assert(n == 24, "*=")
n /= 4
assert(n == 6, "/=")
n //= 4
assert(n == 1, "//=")
n = 7
n %= 4
assert(n == 3, "%=")
n ^= 2
assert(n == 9, "^=")
n = 1
n <<= 4
assert(n == 16, "<<=")
n >>= 2
assert(n == 4, ">>=")
n |= 3
assert(n == 7, "|=")
n &= 5
assert(n == 5, "&=")
local s = "a"
s ..= "b"
assert(s == "ab", "..=")
local maybe = nil
maybe ??= "default"
assert(maybe == "default", "??= should fill nil")
maybe ??= "other"
assert(maybe == "default", "??= should keep non-nil")
obj.n += 1
assert(obj.n == 6, "+= on a member")
local arr = {1, 2}
arr[1] += 10
assert(arr[1] == 11, "+= on an index")
print("assignment ok")