Why not use: x = !x;?

in0 · November 5, 2021, 6:19am

Related discussion:

Breakage caused by PinStatus and PinMode types

opened 10:33PM - 02 Jan 19 UTC

This project changes `LOW`, `HIGH`, `INPUT`, `INPUT_PULLUP`, and `OUTPUT` from m…acros to enums: https://github.com/arduino/ArduinoCore-API/blob/e1eb8de126786b7701b211332dda3f09aa400f35/api/Common.h#L10-L23 I'm concerned that this will cause breakage of a significant amount of existing code. An example is the popular [Keypad library](https://playground.arduino.cc/code/keypad). Compilation of both the [original](https://playground.arduino.cc/uploads/Code/keypad.zip) library and the [version in Library Manager](https://github.com/Chris--A/Keypad) fails once this change is made. ``` In file included from E:\electronics\arduino\libraries\Keypad-master\examples\HelloKeypad\HelloKeypad.ino:10:0: E:\electronics\arduino\libraries\Keypad-master\src/Keypad.h: In member function 'virtual void Keypad::pin_write(byte, boolean)': E:\electronics\arduino\libraries\Keypad-master\src/Keypad.h:81:81: error: cannot convert 'boolean {aka bool}' to 'PinStatus' for argument '2' to 'void digitalWrite(pin_size_t, PinStatus)' virtual void pin_write(byte pinNum, boolean level) { digitalWrite(pinNum, level); } ``` This commonly used code will also now fail: ```c++ digitalWrite(13, !digitalRead(13)); // toggle pin 13 ``` ``` toggle:2:36: error: cannot convert 'bool' to 'PinStatus' for argument '2' to 'void digitalWrite(pin_size_t, PinStatus)' digitalWrite(13, !digitalRead(13)); // toggle pin 13 ``` I understand that the root cause of these errors is bad code and that any code which followed best practices will have no problems with this change. However, I fear there is a lot of bad code in widespread use that currently works fine. In the case of the Keypad library, it is unlikely it can even be fixed since Chris--A has gone AWOL. I'm sure there are other such abandoned projects. I do like the spirit of this change (though lumping `CHANGE`, `FALLING`, and `RISING` into `PinStatus` is questionable). I'm open to being convinced that it's worth the breakage and, if so, I'm willing to help ease the transition by providing user support and submitting PRs to fix broken code. I just think this warrants some consideration before ArduinoCore-API goes into more widespread use. Some previous discussion on the topic: - http://forum.arduino.cc/index.php?topic=455579 (from [here](http://forum.arduino.cc/index.php?topic=455579.msg4001965#msg4001965) onward) - https://forum.arduino.cc/index.php?topic=584322 - http://forum.arduino.cc/index.php?topic=602250 - https://forum.arduino.cc/index.php?topic=621429 - https://forum.arduino.cc/index.php?topic=627883.msg4319254#msg4319254 - https://forum.arduino.cc/index.php?topic=659624 - https://github.com/arduino/ArduinoCore-megaavr/issues/68

The first production release with CHANGE was ArduinoCore-API 1.1.0:
https://github.com/arduino/ArduinoCore-API/commit/445594a6107b4f201675338221fb704d7638a863

So you can use the ARDUINO_API_VERSION macro for this purpose:
https://github.com/arduino/ArduinoCore-API/blob/1.1.0/api/ArduinoAPI.h#L24

#if !defined(ARDUINO_API_VERSION) || ARDUINO_API_VERSION < 10100
// handle absence of CHANGE
#endif

Topic		Replies	Views
Not understanding toggle code Programming	33	10854	May 5, 2021
Conditional in digitalWrite()? Programming	35	8869	May 5, 2021
Using digitalWrite(x, !digitalRead(x)) to toggle a pin in OUTPUT mode Programming	135	5403	September 21, 2023
Are digital pin states acting as boolean values indended or a misfeature? Programming	10	4623	May 5, 2021
Correct use of digital read and bool General Discussion	168	3013	April 17, 2024

Why not use: x = !x;?

Related topics