-- test 1: bitwise and, or, xor
local a = 0b1100
local b = 0b1010
assert((a & b) == 0b1000, "expected 12 & 10 == 8")
assert((a | b) == 0b1110, "expected 12 | 10 == 14")
assert((a ~ b) == 0b0110, "expected 12 ~ 10 == 6")
assert((0xFF & 0x0F) == 0x0F, "hex bitwise and")
assert((0xF0 | 0x0F) == 0xFF, "hex bitwise or")
assert((0xAA ~ 0x55) == 0xFF, "hex bitwise xor")
-- test 2: bitwise not (unary ~)
assert(~0 == -1, "expected ~0 == -1")
assert(~1 == -2, "expected ~1 == -2")
assert(~(-1) == 0, "expected ~(-1) == 0")
assert(~(-2) == 1, "expected ~(-2) == 1")
assert(~~42 == 42, "double bitwise not")
-- test 3: bitwise shifts
assert((1 << 4) == 16, "shift left 1 << 4 == 16")
assert((16 >> 2) == 4, "shift right 16 >> 2 == 4")
assert((16 << -2) == 4, "negative left shift acts as right shift")
assert((4 >> -2) == 16, "negative right shift acts as left shift")
-- test 4: bitwise precedence
-- & binds tighter than |
assert((1 | 2 & 2) == 3, "precedence: 1 | (2 & 2) == 3")
-- ~ (binary xor) binds tighter than |
assert((1 | 2 ~ 3) == 1, "precedence: 1 | (2 ~ 3) == 1")
-- unary ~ binds tightest
assert((~1 & 1) == 0, "precedence: (~1) & 1 == 0")
-- test 5: floats truncation in bitwise
assert((12.7 & 10.2) == 8, "float truncation in bitwise and")
assert(~1.9 == -2, "float truncation in bitwise not")
-- the bit library wraps negative and oversized numbers modulo 2^32
local minusEight = -8
assert(bit.rshift(minusEight, 1) == 0x7ffffffc, "rshift treats negatives as unsigned words")
assert(bit.rshift(-8, 1) == 0x7ffffffc, "constant folding agrees")
assert(bit.band(-1, 0xff) == 0xff, "band wraps negatives")
assert(bit.tobit(2 ^ 32 + 5) == 5 and bit.tobit(0xffffffff) == -1, "tobit keeps the low 32 bits, signed")
print("[pass] bitwise operators (and, or, xor, not, shifts) verified")