Hello Adam,
> hi everyone, i'm new in c programming. i tried to read sources but stuck with
> enum.
> as i know, enum is mainly used to assign names to integral constants. but i
> don't understand, for example, this code
> ----------------------------------------------
> enum term_mode {
> MODE_WRAP = 1 << 0,
> MODE_INSERT = 1 << 1,
> MODE_ALTSCREEN = 1 << 2,
> MODE_CRLF = 1 << 3,
> MODE_ECHO = 1 << 4,
> MODE_PRINT = 1 << 5,
> MODE_UTF8 = 1 << 6,
> };
> ----------------------------------------------
I am assuming you don't know what '<<' does?
The '<<' Operator (as well as '>>') is a bit shifting operator.
In a nutshell, it shifts the binary representation of the number on the
left by the number of places on the right.
This is equivalent to taking the number on the right and multiplying
that often by 2 (or dividing in case of '>>').
For a better explaination see the GNU C manual:
https://www.gnu.org/software/gnu-c-manual/gnu-c-manual.html#Bit-Shifting
> why not simply write ?
> ----------------------------------------------
> enum term_mode {
> MODE_WRAP = 1,
> MODE_INSERT = 2,
> MODE_ALTSCREEN = 4,
> MODE_CRLF = 8,
> MODE_ECHO = 16,
> MODE_PRINT = 32,
> MODE_UTF8 = 64,
> };
> ----------------------------------------------
This is completely equivalent in terms of generated machine code.
I would argue however, that the first case is easier for humans to read
(if you understand the operator) and write.
Especially for higher powers of 2, it is much easier to make a mistake.
Regards,
Jona
