Number formatting

This one uses a pattern string instead of the format! style.

Localization

Localization is done with [NumberSymbols]. The locale-data is provided by pure_rust_locales.

Requirements

A number for this library is any type that is LowerExp + Display. The conversion to string is done via format!("{}") and format!("{:e}"), this string is split at '.' and 'e' and pattern is applied. The digits themselves are not validated to safe time.

Parsing needs FromStr.

• parse_sym() only takes the symbols and removes everything from the input, that is not a digit or the decimal-separator. The result is handed to FromStr.
• parse_fmt() takes a NumberFormat and requires an exact match for the pattern. The recognized parts are reassembled in the correct order and handed to FromStr.

Example

use format_num_pattern::Locale::de_AT_euro;
use format_num_pattern as num;
use format_num_pattern::{NumberFormat, NumberSymbols};

// formats accordingly, uses the default symbols.
let s = num::format(4561.2234, "###,##0.00").expect("works");
assert_eq!(s, "  4,561.22");

// uses symbols
let sym = NumberSymbols::monetary(de_AT_euro);
let s = num::formats(4561.2234, "$ ###,##0.00", &sym).expect("works");
assert_eq!(s.as_str(), "€   4\u{202f}561,22");

// prepared format
let sym = NumberSymbols::monetary(de_AT_euro);
let m2 = NumberFormat::news("$ ###,##0.00", sym).expect("works");

let s = m2.fmt(4561.2234).expect("works");
assert_eq!(s.as_str(), "€   4\u{202f}561,22");

// postfix fmt using the FormatNumber trait
use format_num_pattern::DisplayNumber;
println!("combined output: {}", 4561.2234f64.fmt(&m2));

Patterns

The following patterns are recognized:

• 0 - digit or 0
• 9 - digit or space
• # - digit or sign or space
• - - sign; show space for positive
• + - sign; show '+' for positive and '-' for negative. not localized.
• . - decimal separator
• : - decimal separator, always shown
• , - grouping separator. Might be completely absent, if the FormatSymbols say so.
• E - upper case exponent
• e - lower case exponent
• - space can be used as separator
• '$' - currency. variable length output according to the currency-symbol.
• \ - all ascii characters (ascii 32-128!) are reserved and must be escaped.
• _ - other unicode characters can be used without escaping.

Performance

The simple benchmark that I ran gives a time of

• 1.68 x format!
• 3.5 x ryu