enum is this a bug?

Projects Programming
1

I step through an array of pin numbers to scan multiple input with non sequential pin numbers.

I set this up using enum for scanning a bunch of pushbuttons.

enum buttonNames          { Button0, Button1, Button2, Button3, Button4, Button5, Button6, Button7};
const int buttonPinNo[] = {   1,       0,       2,      4,      3,        9 ,      6,         7  };

This first example works fine.

For a different project I wanted to use shorter names for the buttons and wrote it this way:

enum      buttonNames   { PB1, PB2, PB3, PB4, PB5 };
const int buttonPin[] = { 1,   0,   2,   3,    4 };

It gives an error for the labels PB1,PB2, etc. Any other form is acceptable Is upper case PB followed by a single numeral a keyword of some kind?

The following combinations do not cause an error

enum      buttonNames   { Pb1, pB2, pb3, PBa4, PB45 };
const int buttonPin[] = { 1,   0,   2,   3,    4 };

It is an easy work around but I am curious why that particular combination of characters does not work.

2

It gives an error for the labels PB1,PB2, etc.

There'll be a big clue in the error message.

3

If that clue isn't enough, then beware generally of using short names where the letters are in capitals and which could conflict with existing system macro names.

4

The question is, do these conflict with some system names? The error message does not indicate a conflict but looks like it doesn't recognize an identifier but it is the message given when a keyword is used. It is only a problem when the digit is 0 thru 7.

Just in case something else in my code was causing a problem I created the following empty sketch:

enum names { PB1, PB2,  PB3 };
void setup() {
  // put your setup code here, to run once:
}
void loop() {
  // put your main code here, to run repeatedly:
}

Here is the error.

Enum_Test:4:14: error: expected identifier before numeric constant
enum names { PB1, PB2, PB3 };
^

5

Try Serial.print( PB1 ) ; and see what you get without defining PB1.

The format of enum the compiler thinks you are attempting is:

enum names { MYFIRST = 1 , MYSECOND = 2 .... } ;

It has resolved PB1 to a numeric constant (e.g. 1 ) and is missing the identifier ( e.g. MYFIRST ) .