Macro dmntk_feel::value_null

macro_rules! value_null {
    ($f : expr, $($a : tt) *) => { ... };
    ($l : expr) => { ... };
    () => { ... };
}

Creates Value::Null with optional tracing message.

Examples

use crate::dmntk_feel::{value_null, values::Value};

let v = value_null!();
assert_eq!("null", v.to_string());

let v = value_null!("missing input parameter");
assert_eq!("null(missing input parameter)", v.to_string());

let v = value_null!("integer out of range {}..{}", 1, 100);
assert_eq!("null(integer out of range 1..100)", v.to_string());