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#[derive(Clone, Debug)]
pub enum Value<T> {
Const(T),
Column(usize),
}
impl<T> Value<T> {
pub fn value<'a>(&'a self, row: &'a [T]) -> &'a T {
match *self {
Value::Column(i) => &row[i],
Value::Const(ref val) => val,
}
}
}
#[derive(Clone, Debug)]
pub enum Comparison<T: PartialOrd> {
Equal(Value<T>),
}
impl<T: PartialOrd> Comparison<T> {
pub fn matches(&self, value: &T, row: &[T]) -> bool {
match *self {
Comparison::Equal(ref v) => value == v.value(row),
}
}
}
#[derive(Clone, Debug)]
pub struct Condition<T: PartialOrd> {
pub column: usize,
pub cmp: Comparison<T>,
}
impl<T: PartialOrd> Condition<T> {
pub fn matches(&self, row: &[T]) -> bool {
self.cmp.matches(&row[self.column], row)
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn value() {
assert_eq!(Value::Column(0).value(&["a"]), &"a");
assert_eq!(Value::Const("a").value(&["b"]), &"a");
}
#[test]
fn cmp_eq() {
assert!(Comparison::Equal(Value::Column(0)).matches(&"a", &["a"]));
assert!(!Comparison::Equal(Value::Column(0)).matches(&"a", &["b"]));
assert!(Comparison::Equal(Value::Const("a")).matches(&"a", &["b"]));
assert!(!Comparison::Equal(Value::Const("b")).matches(&"a", &["a"]));
}
#[test]
fn cond_eq() {
let cmpf0 = Comparison::Equal(Value::Column(0));
let cmpca = Comparison::Equal(Value::Const("a"));
let cmpcb = Comparison::Equal(Value::Const("b"));
let cf10 = Condition {
column: 1,
cmp: cmpf0,
};
let cca = Condition {
column: 0,
cmp: cmpca,
};
let ccb = Condition {
column: 0,
cmp: cmpcb,
};
assert!(cf10.matches(&["a", "a"]));
assert!(!cf10.matches(&["a", "b"]));
assert!(cca.matches(&["a"]));
assert!(!cca.matches(&["b"]));
assert!(ccb.matches(&["b"]));
assert!(!ccb.matches(&["a"]));
}
}