- Calculates the bitwise not of a number.
- The number.
bnot() function inverts all of the bits of a number.
Numbers in PICO-8 are stored using a 32-bit fixed point format, with 16 bits for the integer portion, 16 bits for the fractional portion, and a twos complement representation for negative and positive values. As a result, the bitwise-not of a number tends to be its negative. (
bnot(0) is almost 0, but not quite.)
In cases where you're using
bnot() you probably only care about specific bits and not the entire number. You can
band() the result to mask out the bits you don't care about.
Superseded by ~ operator
~ operator added in 0.2.0 performs the same function as
bnot() and is now the recommended way to invert bits, as it uses fewer tokens, costs fewer cycles at runtime, and runs on the real host CPU much more efficiently. Simply replace
-- 0xb = 000...1011 -- not 0xb = 111...0100 -- 0xf = 000...1111 -- (not 0xb) and 0xf = 000...0100 (0x4) print(band(bnot(0xb), 0xf)) -- 4 print(bnot(0xb)) -- -11 (0 - 0xb) print(~0xb) -- preferred method