use crate::constraints::TwoOfThree;
use crate::goals::Goal;
use crate::{
constraints::{Constraint, ResolveFn, VarWatch},
core::{State, Unify, Value},
};
use std::fmt::{self, Debug};
use std::rc::Rc;
pub fn map_2<A, IA, B, IB, C, IC, ABtoC, ACtoB, BCtoA>(
a: IA,
b: IB,
c: IC,
ab_to_c: ABtoC,
ac_to_b: ACtoB,
bc_to_a: BCtoA,
) -> Map2<A, B, C>
where
A: Unify,
B: Unify,
C: Unify,
IA: Into<Value<A>>,
IB: Into<Value<B>>,
IC: Into<Value<C>>,
ABtoC: Fn(&A, &B) -> C + 'static,
ACtoB: Fn(&A, &C) -> B + 'static,
BCtoA: Fn(&B, &C) -> A + 'static,
{
Map2 {
a: a.into(),
b: b.into(),
c: c.into(),
ab_to_c: Rc::new(ab_to_c),
ac_to_b: Rc::new(ac_to_b),
bc_to_a: Rc::new(bc_to_a),
}
}
#[allow(clippy::type_complexity)]
pub struct Map2<A: Unify, B: Unify, C: Unify> {
a: Value<A>,
b: Value<B>,
c: Value<C>,
ab_to_c: Rc<dyn Fn(&A, &B) -> C>,
ac_to_b: Rc<dyn Fn(&A, &C) -> B>,
bc_to_a: Rc<dyn Fn(&B, &C) -> A>,
}
impl<A: Unify, B: Unify, C: Unify> Debug for Map2<A, B, C> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "Map2 {:?} {:?} {:?}", self.a, self.b, self.c)
}
}
impl<A: Unify, B: Unify, C: Unify> Clone for Map2<A, B, C> {
fn clone(&self) -> Self {
Self {
a: self.a.clone(),
b: self.b.clone(),
c: self.c.clone(),
ab_to_c: self.ab_to_c.clone(),
ac_to_b: self.ac_to_b.clone(),
bc_to_a: self.bc_to_a.clone(),
}
}
}
impl<A: Unify, B: Unify, C: Unify> Goal for Map2<A, B, C> {
fn apply(&self, state: State) -> Option<State> {
state.constrain(Rc::new(self.clone()))
}
}
impl<A: Unify, B: Unify, C: Unify> Constraint for Map2<A, B, C> {
fn attempt(&self, state: &State) -> Result<ResolveFn, VarWatch> {
let resolved = TwoOfThree::resolve(&self.a, &self.b, &self.c, state)?;
match resolved {
TwoOfThree::AB(a, b, c) => {
let f = self.ab_to_c.clone();
Ok(Box::new(move |state| {
state.unify(&Value::new(f(&*a, &*b)), &c)
}))
}
TwoOfThree::BC(a, b, c) => {
let f = self.bc_to_a.clone();
Ok(Box::new(move |state| {
state.unify(&Value::new(f(&*b, &*c)), &a)
}))
}
TwoOfThree::AC(a, b, c) => {
let f = self.ac_to_b.clone();
Ok(Box::new(move |state| {
state.unify(&Value::new(f(&*a, &*c)), &b)
}))
}
}
}
}
#[cfg(test)]
mod tests {
use super::map_2;
use crate::core::{LVar, Query};
use crate::goals::both::both;
use crate::goals::unify;
#[test]
fn succeeds() {
let x = LVar::new();
let y = LVar::new();
let z = LVar::new();
let goal = both(
both(both(unify(1, x), unify(2, y)), unify(3, z)),
map_2(x, y, z, |x, y| x + y, |x, z| z - x, |y, z| z - y),
);
assert_eq!(goal.query((x, y)).collect::<Vec<_>>(), vec![(1, 2)]);
}
}