Function parse_key_val 

pub fn parse_key_val<T, U>(
    value: &str,
) -> Result<(T, U), Box<dyn Error + Send + Sync + 'static>>
where
    T: FromStr,
    T::Err: Error + Send + Sync + 'static,
    U: FromStr,
    U::Err: Error + Send + Sync + 'static,

Parse a single key-value pair string. This is used to parse command line arguments.

use reqlang_expr::cliutil::parse_key_val;

let a = parse_key_val::<String, String>("a=1");

assert_eq!(("a".to_string(), "1".to_string()), a.unwrap());

Example of using parse_key_val with Clap

use clap::Parser;
use reqlang_expr::cliutil::parse_key_val;

#[derive(Parser, Debug)]
struct Args {
    #[arg(long, value_delimiter = ' ', num_args = 1.., value_parser = parse_key_val::<String, String>)]
    vars: Vec<(String, String)>
}

let args = Args::parse_from(["test", "--vars", "key=value", "another_key=another_value"]);
assert_eq!(args.vars, vec![("key".to_string(), "value".to_string()), ("another_key".to_string(), "another_value".to_string())]);