const PRINTER vs. static PARSER

[tisonkun]

In the code examples under fmt module, I observe a consistent pattern to use const PRINTERand static PARSER.

Since both of them has a constant new constructor, is there any specific consideration to distinguish them? Or just a coincidence.

cc @BurntSushi

[BurntSushi]

I probably wasn't too careful about it. For the most part it doesn't matter too much, with these two caveats:

• If you can use static, you probably should. With static, there's only ever one copy of the data in the binary. With const, everything gets inlined at each use. That is, with const, you get no single fixed memory address for your data. But with static you do.
• If you need to initialize a printer/parser in a const context, then use const.

[tisonkun]

Thanks for your explanation! This aligns with my understanding :D