use crate::core::State;
use crate::goals::Goal;
/** A [`Goal`] that always succeeds.
# Example
```
use canrun::{Succeed, unify, Value, all, Query};
let x = Value::var();
let goal = all![unify(x.clone(), 1), Succeed];
let result: Vec<_> = goal.query(x).collect();
assert_eq!(result, vec![1])
```
*/
#[derive(Debug)]
pub struct Succeed;
impl Goal for Succeed {
fn apply(&self, state: State) -> Option<State> {
Some(state)
}
}
#[cfg(test)]
mod test {
use super::*;
#[test]
fn succeed() {
let state = State::new();
let goal = Succeed;
let result = goal.apply(state);
assert!(result.is_some());
}
}