How to implement Zero FillRight Shift (>>>)? Topic is solved

[afe]

Hello,

How to implement JS Zero FillRight Shift (>>>) with AHK?

JavaScript (Zero Fill) Right Shift (>>>)
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Bitwise_Operators#%3E%3E%3E_(Zero-fill_right_shift)

[just me]

Code: Select all

#NoEnv
ToShift := 9
MsgBox, 0, ZeroFillRightShift32, % ToShift . " >> 2 = " . ZeroFillRightShift32(ToShift, 2)
ToShift := -9
MsgBox, 0, ZeroFillRightShift32, % ToShift . " >> 2 = " . ZeroFillRightShift32(ToShift, 2)
ExitApp

ZeroFillRightShift32(Num, Shift) {
   Return ((Num & 0xFFFFFFFF) >> Shift)
}

[afe]

Great! Just need to perform & operation with 0xFFFFFFFF, why ?

Code: Select all

msgbox % ( -9 & 0xFFFFFFFF ) >> 2

[just me]

AHK stores all integer values as 64-bit signed integers (Int64). All negative integers have bit 63 (bits are counted from 0 to 63) set to 1 (0x8000000000000000). When shifted to the right, AHK restores this sign bit after each bit shift.
Var & 0xFFFFFFFF clears the contents of the bits 32 - 63, i.e. sets the sign bit to 0. That's why righ-shifting refills the sign bit with 0 after shifting.

[afe]

Exactly. Thank you very much!