Shl

Superseded / Deprecated

The feature described in this article has been superseded by a newer feature. This feature still works in PICO-8, but the new feature should be used instead. See the article's "Superseded by..." section for specific details.

shl( num, bits )

Shifts the bits of a number to the left.

num

The number.

bits

The number of bits to shift.

The shl() function takes a number and a bit count, and returns the result of shifting the bits of the number to the left by that count.

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. Bit shifting uses the entire number representation. (See examples below.)

Superseded by >> operator

The << operator added in 0.2.0 performs the same function as shl() and is now the recommended way to shift bits left, as it uses fewer tokens, costs fewer cycles at runtime, and runs on the real host CPU much more efficiently. Simply replace shl(a,b) with a<<b.

Examples

-- 1 = 00000001 binary
-- 8 = 00001000 binary
print(shl(1, 3))      -- 8

-- 0.125 = 0000.0010 binary
-- 1.000 = 0001.0000 binary
print(shl(0.125, 3))  -- 1

print(1 << 3)         -- 8, preferred method

See also

• Math
• band()
• bor()
• bxor()
• bnot()
• lshr()
• shr()
• rotl()
• rotr()