Function add_tone 

pub fn add_tone(syllable: &mut Syllable, tone_mark: &ToneMark) -> Transformation

Add tone mark to input.

Returns the result of the transformation operation.

Examples

use vi::{Syllable, processor::{add_tone, ToneMark, Transformation}};

let mut syllable = Syllable::new("hello");
let result = add_tone(&mut syllable, &ToneMark::Acute);
assert_eq!(result, Transformation::ToneMarkAdded);