fee 0.2.4

Expression evaluator supporting numeric, logical and bitwise operators
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42

use crate::{
    prelude::*,
    resolver::{Locked, LockedResolver, ResolverState, Unlocked, UnlockedResolver},
};

/// A resolver that does not resolve any values.
///
/// Every call to [`Resolver::resolve()`] returns `None`.
/// This resolver is useful when expressions do not contain any variables or function calls.
pub struct EmptyResolver<S>
where
    S: ResolverState,
{
    _state: S,
}

impl<T> LockedResolver<T> for EmptyResolver<Locked> {}
impl<T> UnlockedResolver<T, EmptyResolver<Locked>> for EmptyResolver<Unlocked>
{
    fn lock(self) -> EmptyResolver<Locked>
    {
        EmptyResolver { _state: Locked }
    }
}

impl<S, T> Resolver<S, T> for EmptyResolver<S>
where
    S: ResolverState,
{
    fn resolve(&self, _name: &str) -> Option<&T>
    {
        None
    }
}

impl EmptyResolver<Unlocked>
{
    pub fn new() -> Self
    {
        EmptyResolver { _state: Unlocked }
    }
}