// include the latest version of the regex crate in your Cargo.toml
extern crate regex;
use regex::Regex;
fn main() {
let regex = Regex::new(r#"(?m)(?x) # free-spacing mode
(?(DEFINE)
# Within this DEFINE block, we'll define many subroutines
# They build on each other like lego until we can define
# a "big number"
(?<one_to_9>
# The basic regex:
# one|two|three|four|five|six|seven|eight|nine
# We'll use an optimized version:
# Option 1: four|eight|(?:fiv|(?:ni|o)n)e|t(?:wo|hree)|
# s(?:ix|even)
# Option 2:
(?:f(?:ive|our)|s(?:even|ix)|t(?:hree|wo)|(?:ni|o)ne|eight)
) # end one_to_9 definition
(?<ten_to_19>
# The basic regex:
# ten|eleven|twelve|thirteen|fourteen|fifteen|sixteen|seventeen|
# eighteen|nineteen
# We'll use an optimized version:
# Option 1: twelve|(?:(?:elev|t)e|(?:fif|eigh|nine|(?:thi|fou)r|
# s(?:ix|even))tee)n
# Option 2:
(?:(?:(?:s(?:even|ix)|f(?:our|if)|nine)te|e(?:ighte|lev))en|
t(?:(?:hirte)?en|welve))
) # end ten_to_19 definition
(?<two_digit_prefix>
# The basic regex:
# twenty|thirty|forty|fifty|sixty|seventy|eighty|ninety
# We'll use an optimized version:
# Option 1: (?:fif|six|eigh|nine|(?:tw|sev)en|(?:thi|fo)r)ty
# Option 2:
(?:s(?:even|ix)|t(?:hir|wen)|f(?:if|or)|eigh|nine)ty
) # end two_digit_prefix definition
(?<one_to_99>
(?&two_digit_prefix)(?:[- ](?&one_to_9))?|(?&ten_to_19)|
(?&one_to_9)
) # end one_to_99 definition
(?<one_to_999>
(?&one_to_9)[ ]hundred(?:[ ](?:and[ ])?(?&one_to_99))?|
(?&one_to_99)
) # end one_to_999 definition
(?<one_to_999_999>
(?&one_to_999)[ ]thousand(?:[ ](?&one_to_999))?|
(?&one_to_999)
) # end one_to_999_999 definition
(?<one_to_999_999_999>
(?&one_to_999)[ ]million(?:[ ](?&one_to_999_999))?|
(?&one_to_999_999)
) # end one_to_999_999_999 definition
(?<one_to_999_999_999_999>
(?&one_to_999)[ ]billion(?:[ ](?&one_to_999_999_999))?|
(?&one_to_999_999_999)
) # end one_to_999_999_999_999 definition
(?<one_to_999_999_999_999_999>
(?&one_to_999)[ ]trillion(?:[ ](?&one_to_999_999_999_999))?|
(?&one_to_999_999_999_999)
) # end one_to_999_999_999_999_999 definition
(?<bignumber>
zero|(?&one_to_999_999_999_999_999)
) # end bignumber definition
(?<zero_to_9>
(?&one_to_9)|zero
) # end zero to 9 definition
(?<decimals>
point(?:[ ](?&zero_to_9))+
) # end decimals definition
) # End DEFINE
####### The Regex Matching Starts Here ########
^(?&bignumber)(?:[ ](?&decimals))?$
### Other examples of groups we could match ###
#(?&bignumber)
# (?&one_to_99)
# (?&one_to_999)
# (?&one_to_999_999)
# (?&one_to_999_999_999)
# (?&one_to_999_999_999_999)
# (?&one_to_999_999_999_999_999)"#).unwrap();
let string = "one trillion
seven hundred twenty two
7even
zero point nine five
nine hundred ninety nine thousand two hundred thirteen";
// result will be an iterator over tuples containing the start and end indices for each match in the string
let result = regex.captures_iter(string);
for mat in result {
println!("{:?}", mat);
}
}
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Rust, please visit: https://docs.rs/regex/latest/regex/