Some string constants

1

Perhaps I've already asked in past. In the Python std lib there's the 'string' module:
https://docs.python.org/3/library/string.html

It contains some constants:

string.ascii_letters
string.ascii_lowercase
string.ascii_uppercase
string.digits

Is it a good idea to add such constants to rust stdlib too?

Currently you could generate them like this in user code:

let ascii_lowercase: String = (b'a' ..= b'z').map(char::from).collect();
let ascii_uppercase: String = (b'A' ..= b'Z').map(char::from).collect();
let ascii_letters = ascii_lowercase + &ascii_uppercase;
let digits: String = (b'0' ..= b'9').map(char::from).collect();
2

i think this is left out for the same reason that date formatting is left out of the standard library and to external crates: for some purposes one might want to make the definition of lowercase/uppercase depend on the locale, for others it needs to be deterministic, just too many variations and interpretation—why would ASCII be special?

3

The standard library does have corresponding methods like is_ascii_lowercase.

4

oh! yes then it's arguably a small step to exposing them in some other way

5

What would you use them for? When are they better than the ranges, or the predicates that already exist?