Binary flags - Revision history

Sergeirocks100: 20 revisions imported

2022-01-19T16:35:18Z

20 revisions imported

← Older revision

Revision as of 16:35, 19 January 2022

tgstation>Rohesie at 02:16, 27 January 2021

2021-01-27T02:16:39Z

← Older revision		Revision as of 02:16, 27 January 2021
Line 381:		Line 381:

	/mob		/mob
	var/disabilities = 0		var/disabilities = NONE

	/mob/proc/add_disability(~~var/~~dis)		/mob/proc/add_disability(dis)
	disabilities \|= dis		disabilities \|= dis

	/mob/proc/check_disability(~~var/~~dis)		/mob/proc/check_disability(dis)
	if( disabilities & dis )		if( disabilities & dis )
	return 1		return TRUE
	else		else
	return 0		return FALSE

	/mob/proc/remove_disability(~~var/~~dis)		/mob/proc/remove_disability(dis)
	disabilities &= ~dis		disabilities &= ~dis


	{{Contribution guides}}		{{Contribution guides}}

tgstation>Oranges: /* Operations in binary */

2021-01-12T07:38:22Z

Operations in binary

← Older revision		Revision as of 07:38, 12 January 2021
Line 63:		Line 63:
	=== Operations in binary ===		=== Operations in binary ===

	What can we do with these numbers ~~tho~~? There are 3 binary operators available in byond: And (&), Or (\|) and Not (~). NOTE: These are binary operators, which means they do the operation on each individual bit.		What can we do with these numbers though? There are 3 binary operators available in byond: And (&), Or (\|) and Not (~). NOTE: These are binary operators, which means they do the operation on each individual bit.

	A good way to understand how these work is to not think of these 1s and 0s as numbers, but as truth and lies (false). So wherever you have a 1, you can substitute it with a true statement, while where you have a 0 you substitute it with a lie (a false statement).		A good way to understand how these work is to not think of these 1s and 0s as numbers, but as truth and lies (false). So wherever you have a 1, you can substitute it with a true statement, while where you have a 0 you substitute it with a lie (a false statement).

tgstation>Oranges: /* Toggling bitflags */

2021-01-12T07:35:54Z

Toggling bitflags

← Older revision		Revision as of 07:35, 12 January 2021
Line 303:		Line 303:
	* where the right hand side of the XOR is a 0, it will leave the left hand side values unchanged in the final output		* where the right hand side of the XOR is a 0, it will leave the left hand side values unchanged in the final output

	If you refer back to the [[Binary_flags#Binary_Xor_.28_.5E_.29 \| XOR truth table]]~~, specifically,~~ the truth table entries that deal with a 1 on the right hand side of the ~~xor~~ operation		If you refer back to the [[Binary_flags#Binary_Xor_.28_.5E_.29 \| XOR truth table]] you can see these principles clearly

			First the truth table entries that deal with a 1 on the right hand side of the XOR operation
	* 0 ^ 1 = 1		* 0 ^ 1 = 1
	* 1 ^ 1 = 0		* 1 ^ 1 = 0
	~~You can see they are flipping~~ the ~~result bit to be~~ the ~~opposite of whatever was set in the left~~ hand side of the operation.		Then the truth table entries that deal with a 0 on the right hand side of the XOR operation
			* 0 ^ 0 = 0
			* 1 ^ 0 = 1


	To help illustrate this concept, lets do an example where the user has the DISABILITY_ARM and the DISABILITY_EAR flags set and we want to toggle the DISABILITY_ARM flag to be the opposite of whatever it was before		To help illustrate this concept, lets do an example where the user has the DISABILITY_ARM and the DISABILITY_EAR flags set and we want to toggle the DISABILITY_ARM flag to be the opposite of whatever it was before

tgstation>Oranges: /* Toggling bitflags */

2021-01-12T07:33:48Z

Toggling bitflags

← Older revision		Revision as of 07:33, 12 January 2021
Line 299:		Line 299:
	Sometimes, you want to toggle a bitflag, that is, if the bit on the flag is 1, you want to set it to 0, and if the bit is 0, you want to set it to 1		Sometimes, you want to toggle a bitflag, that is, if the bit on the flag is 1, you want to set it to 0, and if the bit is 0, you want to set it to 1

	You can use the ~~xor~~ function to do this due to the following properties		You can use the XOR function to do this due to the following properties
	* where the right hand side of the XOR is a 1, it will "toggle" the bits on the left hand side in the final output		* where the right hand side of the XOR is a 1, it will "toggle" the bits on the left hand side in the final output
	* where the right hand side of the XOR is a 0, it will leave the left hand side values unchanged in the final output		* where the right hand side of the XOR is a 0, it will leave the left hand side values unchanged in the final output

tgstation>Oranges: /* Toggling bitflags */

2021-01-12T07:33:09Z

Toggling bitflags

← Older revision		Revision as of 07:33, 12 January 2021
Line 299:		Line 299:
	Sometimes, you want to toggle a bitflag, that is, if the bit on the flag is 1, you want to set it to 0, and if the bit is 0, you want to set it to 1		Sometimes, you want to toggle a bitflag, that is, if the bit on the flag is 1, you want to set it to 0, and if the bit is 0, you want to set it to 1

	You can use the xor function to do this ~~trivially,~~ due to the following properties		You can use the xor function to do this due to the following properties
	* where the right hand side of the XOR is a 1, it will "toggle" the bits on the left hand side in the final output		* where the right hand side of the XOR is a 1, it will "toggle" the bits on the left hand side in the final output
	* where the right hand side of the XOR is a 0, it will leave the left hand side values unchanged in the final output		* where the right hand side of the XOR is a 0, it will leave the left hand side values unchanged in the final output
Line 308:		Line 308:
	You can see they are flipping the result bit to be the opposite of whatever was set in the left hand side of the operation.		You can see they are flipping the result bit to be the opposite of whatever was set in the left hand side of the operation.

			To help illustrate this concept, lets do an example where the user has the DISABILITY_ARM and the DISABILITY_EAR flags set and we want to toggle the DISABILITY_ARM flag to be the opposite of whatever it was before
	~~This makes it highly useful for toggling bits, as you can choose easily which bits to toggle (by setting them to 1 in the right hand side of the xor operations inputs)~~

	~~Consider the following case~~, where the user has the DISABILITY_ARM and the DISABILITY_EAR flags set and we want to toggle the DISABILITY_ARM flag to be the opposite of whatever it was before

	disabilities = disabilities ^ DISABILITY_ARM		disabilities = disabilities ^ DISABILITY_ARM

tgstation>Oranges: /* Toggling bitflags */

2021-01-12T07:32:23Z

Toggling bitflags

← Older revision		Revision as of 07:32, 12 January 2021
Line 302:		Line 302:
	* where the right hand side of the XOR is a 1, it will "toggle" the bits on the left hand side in the final output		* where the right hand side of the XOR is a 1, it will "toggle" the bits on the left hand side in the final output
	* where the right hand side of the XOR is a 0, it will leave the left hand side values unchanged in the final output		* where the right hand side of the XOR is a 0, it will leave the left hand side values unchanged in the final output
	[[Binary_flags#Binary_Xor_.28_.5E_.29 \| ~~Refer back to~~ the ~~XOR~~ truth table to ~~help see why this is~~ the ~~case]]~~
			If you refer back to the [[Binary_flags#Binary_Xor_.28_.5E_.29 \| XOR truth table]], specifically, the truth table entries that deal with a 1 on the right hand side of the xor operation
			* 0 ^ 1 = 1
			* 1 ^ 1 = 0
			You can see they are flipping the result bit to be the opposite of whatever was set in the left hand side of the operation.


	This makes it highly useful for toggling bits, as you can choose easily which bits to toggle (by setting them to 1 in the right hand side of the xor operations inputs)		This makes it highly useful for toggling bits, as you can choose easily which bits to toggle (by setting them to 1 in the right hand side of the xor operations inputs)

tgstation>Oranges: /* Toggling bitflags */

2021-01-12T07:29:53Z

Toggling bitflags

← Older revision		Revision as of 07:29, 12 January 2021
Line 333:		Line 333:
	RESULT 0b1010		RESULT 0b1010
	</pre>		</pre>
	Final result ~~and~~ the DISABILITY_ARM flag is toggled back on, and DISABILITY_EAR remains unchanged still.		Final result, the DISABILITY_ARM flag is toggled back on, and DISABILITY_EAR remains unchanged still.

	disabilities = 0b1010		disabilities = 0b1010

	XOR can be trivially used then to toggle any specific flag by simply ~~xoring~~ the flag holding variable with the define that represents the bitflag you want to toggle.		XOR can be trivially used then to toggle any specific flag by simply XORING the flag holding variable with the define that represents the bitflag you want to toggle, you can even combine sets of flags to toggle multiple at once

			e.g disabilities = disabilities ^ (DISABILITY_ARM \| DISABILITY_LEG)

	== Shorter forms of writing ==		== Shorter forms of writing ==

tgstation>Oranges: /* Toggling bitflags */

2021-01-12T07:28:48Z

Toggling bitflags

← Older revision		Revision as of 07:28, 12 January 2021
Line 312:		Line 312:
	disabilities = 0b1010 ^ 0b1000		disabilities = 0b1010 ^ 0b1000

	if we run through the XOR truth table for each pair of bits ~~(starting from the least significant bit on the right)~~		if we run through the XOR truth table for each pair of bits horizontally
	*0 ^ 0 = 0		<pre>
	*1 ^ 0 = 1		0b1010
	*0 ^ 0 = 0		XOR 0b1000
	*1 ^ 1 = 0		RESULT 0b0010
			</pre>

	Final result, the flag for DISABILITY_ARM is toggled off, but note that DISABILITY_EAR flag is unchanged, perfect!		Final result, the flag for DISABILITY_ARM is toggled off, but note that DISABILITY_EAR flag is unchanged, perfect!
Line 327:		Line 328:

	disabilities = 0b0010 ^ 0b1000 (note DISABILITY_ARM is currently set to 0)		disabilities = 0b0010 ^ 0b1000 (note DISABILITY_ARM is currently set to 0)
	*0 ^ 0 = 0		<pre>
	*1 ^ 0 = 1		0b0010
	*0 ^ 0 = 0		XOR 0b1000
	*0 ^ 1 = 1		RESULT 0b1010
			</pre>
	Final result and the DISABILITY_ARM flag is toggled back on, and DISABILITY_EAR remains unchanged still.		Final result and the DISABILITY_ARM flag is toggled back on, and DISABILITY_EAR remains unchanged still.

tgstation>Oranges: /* Toggling bitflags */

2021-01-12T07:26:55Z

Toggling bitflags

← Older revision		Revision as of 07:26, 12 January 2021
Line 319:		Line 319:

	Final result, the flag for DISABILITY_ARM is toggled off, but note that DISABILITY_EAR flag is unchanged, perfect!		Final result, the flag for DISABILITY_ARM is toggled off, but note that DISABILITY_EAR flag is unchanged, perfect!

	disabilities = 0b0010		disabilities = 0b0010

Line 332:		Line 333:

	Final result and the DISABILITY_ARM flag is toggled back on, and DISABILITY_EAR remains unchanged still.		Final result and the DISABILITY_ARM flag is toggled back on, and DISABILITY_EAR remains unchanged still.

	disabilities = 0b1010		disabilities = 0b1010