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use crate::constraints::{resolve_2, Constraint, ResolveFn, VarWatch};
use crate::goals::{unify, Goal};
use crate::lvec::LVec;
use crate::{State, Unify, Value};
use std::fmt::Debug;
use std::ops::Range;
use std::rc::Rc;
pub fn slice<T, SV, RV, CV>(slice: SV, range: RV, collection: CV) -> Slice<T>
where
T: Unify,
LVec<T>: Unify,
SV: Into<Value<LVec<T>>>,
RV: Into<Value<Range<usize>>>,
CV: Into<Value<LVec<T>>>,
{
Slice {
slice: slice.into(),
range: range.into(),
collection: collection.into(),
}
}
#[derive(Debug)]
pub struct Slice<T: Unify> {
slice: Value<LVec<T>>,
range: Value<Range<usize>>,
collection: Value<LVec<T>>,
}
impl<T: Unify> Clone for Slice<T> {
fn clone(&self) -> Self {
Self {
slice: self.slice.clone(),
range: self.range.clone(),
collection: self.collection.clone(),
}
}
}
impl<T: Unify> Goal for Slice<T> {
fn apply(&self, state: State) -> Option<State> {
state.constrain(Rc::new(self.clone()))
}
}
impl<T: Unify> Constraint for Slice<T>
where
T: Unify,
{
fn attempt(&self, state: &State) -> Result<ResolveFn, VarWatch> {
let (range, collection) = resolve_2(&self.range, &self.collection, state)?;
let slice_a = self.slice.clone();
let slice_b = collection.vec.get((*range).clone());
match slice_b {
Some(slice_b) => {
let slice_b: LVec<_> = slice_b.into();
Ok(Box::new(move |state| unify(slice_a, slice_b).apply(state)))
}
None => Ok(Box::new(|_| None)), }
}
}
#[cfg(test)]
mod tests {
use crate::goal_vec;
use crate::goals::unify;
use crate::{lvec, LVar};
#[test]
fn basic_slice() {
let x = LVar::new();
let goals = goal_vec![lvec::slice(lvec![x], 0..1, lvec![1, 2, 3])];
goals.assert_permutations_resolve_to(x, vec![1]);
}
#[test]
fn slice_with_lh_var() {
let x = LVar::new();
let goals = goal_vec![unify(x, 3), lvec::slice(lvec![2, x], 1..3, lvec![1, 2, 3])];
goals.assert_permutations_resolve_to(x, vec![3]);
}
#[test]
fn slice_with_rh_var() {
let x = LVar::new();
let goals = goal_vec![unify(x, 3), lvec::slice(lvec![2, 3], 1..3, lvec![1, 2, x])];
goals.assert_permutations_resolve_to(x, vec![3]);
}
#[test]
fn slice_with_out_of_range() {
let x = LVar::new();
let goals = goal_vec![unify(x, 3), lvec::slice(lvec![2, 3], 1..4, lvec![1, 2, x])];
goals.assert_permutations_resolve_to(x, vec![]);
}
#[test]
fn debug_impl() {
let slice = lvec::slice(lvec![2, 3], 1..4, lvec![1, 2, 3]);
assert_ne!(format!("{slice:?}"), "");
}
}