Enum Expression 

pub enum Expression {
    Field(String),
    Literal(Value),
    Comparison {
        left: Box<Expression>,
        operator: Operator,
        right: Box<Expression>,
    },
    And {
        left: Box<Expression>,
        right: Box<Expression>,
    },
    Or {
        left: Box<Expression>,
        right: Box<Expression>,
    },
    Not(Box<Expression>),
    Variable(String),
}

Expression AST node

Variants

Field(String)

Field reference (e.g., “User.IsVIP”, “Order.Amount”)

Literal(Value)

Literal value (e.g., true, false, 42, “hello”)

Comparison

Binary comparison (e.g., “X == Y”, “A > B”)

Fields

left: Box<Expression>

operator: Operator

right: Box<Expression>

And

Logical AND operation (e.g., “A && B”)

Fields

left: Box<Expression>

right: Box<Expression>

Or

Logical OR operation (e.g., “A || B”)

Fields

left: Box<Expression>

right: Box<Expression>

Not(Box<Expression>)

Negation (e.g., “!X”)

Variable(String)

Variable (for future unification support, e.g., “?X”, “?Customer”)

Implementations

impl Expression

pub fn evaluate(&self, facts: &Facts) -> Result<Value>

Evaluate expression against facts

pub fn is_satisfied(&self, facts: &Facts) -> bool

Check if expression is satisfied (returns true/false)

pub fn extract_fields(&self) -> Vec<String>

Extract all field references from expression

pub fn to_string(&self) -> String

Convert to human-readable string

Trait Implementations

impl Clone for Expression

fn clone(&self) -> Expression

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Expression

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl PartialEq for Expression

fn eq(&self, other: &Expression) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl StructuralPartialEq for Expression