Function re_concat 

pub fn re_concat(r1: RegLan, r2: RegLan) -> RegLan

Concatenation of two regular expressions

Example

use aws_smt_strings::smt_regular_expressions::*;

let aaa = str_to_re(&"aaa".into());
let bbb = str_to_re(&"bbb".into());
assert!(str_in_re(&"aaabbb".into(), re_concat(aaa, bbb)));