reval 0.4.5

Simple Rust expression evaluator
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

use crate::{expr::Expr, function::FunctionContext, value::Value, Result};

/// A rule is an expression with a name
#[derive(Debug, Clone, PartialEq)]
pub struct Rule {
    name: String,
    expr: Expr,
}

impl Rule {
    /// Construct a new rule from a name and an expression
    pub fn new(name: impl Into<String>, expr: Expr) -> Self {
        Self {
            name: name.into(),
            expr,
        }
    }

    /// Evaluate a rule on some data using the user-functions provided by the
    /// context
    pub async fn evaluate<'a>(&self, context: &mut FunctionContext<'a>, facts: &Value) -> Outcome {
        Outcome {
            value: self.expr.evaluate(context, facts).await,
            rule: &self.name,
        }
    }

    /// Return the name of the rule
    pub fn name(&self) -> &str {
        &self.name
    }
}

/// The outcome from evaluating a rule.
/// Contains the resulting value from evaluating the rule expression plus
/// metadata. For now the metadata is limited to the name of the rule
pub struct Outcome<'a> {
    pub value: Result<Value>,
    pub rule: &'a str,
}