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use crate::goals::{unify, Goal};
use crate::lvec::LVec;
use crate::state::{
constraints::{resolve_2, Constraint, ResolveFn, VarWatch},
State,
};
use crate::value::{IntoVal, Val};
use crate::{DomainType, UnifyIn};
use std::fmt::Debug;
use std::ops::Range;
pub fn slice<'a, I, SV, RV, CV, D>(slice: SV, range: RV, collection: CV) -> Goal<'a, D>
where
I: UnifyIn<'a, D> + 'a,
LVec<I>: UnifyIn<'a, D>,
SV: IntoVal<LVec<I>>,
RV: IntoVal<Range<usize>>,
CV: IntoVal<LVec<I>>,
D: DomainType<'a, Range<usize>> + DomainType<'a, I> + DomainType<'a, LVec<I>>,
{
Goal::constraint(Slice {
slice: slice.into_val(),
range: range.into_val(),
collection: collection.into_val(),
})
}
#[derive(Debug)]
struct Slice<I: Debug> {
slice: Val<LVec<I>>,
range: Val<Range<usize>>,
collection: Val<LVec<I>>,
}
impl<'a, I, D> Constraint<'a, D> for Slice<I>
where
I: UnifyIn<'a, D> + 'a,
D: DomainType<'a, Range<usize>> + DomainType<'a, I> + DomainType<'a, LVec<I>>,
{
fn attempt(&self, state: &State<'a, D>) -> Result<ResolveFn<'a, D>, 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::example::Collections;
use crate::goals::{unify, Goal};
use crate::lvec;
use crate::util;
use crate::value::var;
#[test]
fn basic_slice() {
let x = var::<i32>();
let goals: Vec<Goal<Collections>> = vec![lvec::slice(lvec![x], 0..1, lvec![1, 2, 3])];
util::assert_permutations_resolve_to(goals, x, vec![1]);
}
#[test]
fn slice_with_lh_var() {
let x = var();
let goals: Vec<Goal<Collections>> =
vec![unify(x, 3), lvec::slice(lvec![2, x], 1..3, lvec![1, 2, 3])];
util::assert_permutations_resolve_to(goals, x, vec![3]);
}
#[test]
fn slice_with_rh_var() {
let x = var();
let goals: Vec<Goal<Collections>> =
vec![unify(x, 3), lvec::slice(lvec![2, 3], 1..3, lvec![1, 2, x])];
util::assert_permutations_resolve_to(goals, x, vec![3]);
}
#[test]
fn slice_with_out_of_range() {
let x = var();
let goals: Vec<Goal<Collections>> =
vec![unify(x, 3), lvec::slice(lvec![2, 3], 1..4, lvec![1, 2, x])];
util::assert_permutations_resolve_to(goals, x, vec![]);
}
#[test]
fn debug_impl() {
let slice: Goal<Collections> = lvec::slice(lvec![2, 3], 1..4, lvec![1, 2, 3]);
assert_ne!(format!("{:?}", slice), "");
}
}