Get rid of the boxed iterator returned from query in favor of impl Iterator

.github/workflows/tests.yml

@@ -31,7 +31,7 @@ jobs:
         uses: actions-rs/toolchain@v1
         with:
           profile: minimal
-          toolchain: 1.70.0
+          toolchain: 1.75.0
           override: true
       - name: Build
         run: cargo build --verbose

canrun/Cargo.toml

@@ -10,7 +10,7 @@ categories = ["algorithms", "mathematics"]
 keywords = ["logic", "dsl", "kanren"]
 license = "MIT/Apache-2.0"
 edition = "2021"
-rust-version = "1.70.0"
+rust-version = "1.75.0"
 
 [dependencies]
 im-rc = "15.1.0"

canrun/src/core/query.rs

@@ -24,7 +24,7 @@ A blanket impl covers anything that implements [`StateIterator`], so many
 types including [`Goal`](crate::goals) and [`State`](crate::State) are
 queryable.
 */
-pub trait Query<'a> {
+pub trait Query {
     /**
     Get [reified](crate::core::Reify) results from things that can produce
     [`StateIter`](crate::core::StateIter)s.
@@ -57,11 +57,11 @@ pub trait Query<'a> {
     assert_eq!(result, vec![1])
     ```
     */
-    fn query<Q: Reify + 'a>(self, query: Q) -> Box<dyn Iterator<Item = Q::Reified> + 'a>;
+    fn query<Q: Reify>(self, query: Q) -> impl Iterator<Item = Q::Reified>;
 }
 
-impl<'a, S: StateIterator + 'a> Query<'a> for S {
-    fn query<Q: Reify + 'a>(self, query: Q) -> Box<dyn Iterator<Item = Q::Reified> + 'a> {
+impl<S: StateIterator> Query for S {
+    fn query<Q: Reify>(self, query: Q) -> impl Iterator<Item = Q::Reified> {
         Box::new(
             self.into_states()
                 .filter_map(move |s| query.reify_in(&s.ready()?)),

canrun/src/goals/both.rs

@@ -5,9 +5,9 @@ use crate::core::State;
 A [Goal](crate::goals::Goal) that only succeeds if both sub-goals succeed. Create with [`both`].
  */
 #[derive(Debug)]
-pub struct Both {
-    a: Box<dyn Goal>,
-    b: Box<dyn Goal>,
+pub struct Both<A: Goal, B: Goal> {
+    a: A,
+    b: B,
 }
 
 /**
@@ -41,14 +41,11 @@ let result: Vec<_> = goal.query(x).collect();
 assert_eq!(result, vec![]) // Empty result
 ```
 */
-pub fn both(a: impl Goal, b: impl Goal) -> Both {
-    Both {
-        a: Box::new(a),
-        b: Box::new(b),
-    }
+pub fn both<A: Goal, B: Goal>(a: A, b: B) -> Both<A, B> {
+    Both { a, b }
 }
 
-impl Goal for Both {
+impl<A: Goal, B: Goal> Goal for Both<A, B> {
     fn apply(&self, state: State) -> Option<State> {
         self.a.apply(state).and_then(|s| self.b.apply(s))
     }

canrun/src/goals/lazy.rs

@@ -5,20 +5,18 @@ use crate::core::State;
 
 use super::Goal;
 
-type LazyFun = dyn Fn() -> Box<dyn Goal>;
-
 /**
 A [Goal](crate::goals::Goal) that is generated via callback just as
 it is about to be evaluated. Create with [`lazy`].
  */
-pub struct Lazy {
-    fun: Rc<LazyFun>,
+pub struct Lazy<G: Goal> {
+    fun: Rc<dyn Fn() -> G>,
 }
 
-impl Debug for Lazy {
+impl<G: Goal> Debug for Lazy<G> {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         f.debug_struct("Lazy")
-            .field("fun", &"Rc<dyn Fn() -> Box<dyn Goal>>")
+            .field("fun", &"Rc<dyn Fn() -> impl Goal>")
             .finish()
     }
 }
@@ -44,14 +42,15 @@ let result: Vec<_> = goal.query(x).collect();
 assert_eq!(result, vec![1])
 ```
 */
-pub fn lazy<F>(fun: F) -> Lazy
+pub fn lazy<F, G>(fun: F) -> Lazy<G>
 where
-    F: (Fn() -> Box<dyn Goal>) + 'static,
+    G: Goal,
+    F: (Fn() -> G) + 'static,
 {
     Lazy { fun: Rc::new(fun) }
 }
 
-impl Goal for Lazy {
+impl<G: Goal> Goal for Lazy<G> {
     fn apply(&self, state: State) -> Option<State> {
         let fun = &self.fun;
         let goal = fun();

canrun/src/goals/mod.rs

@@ -82,3 +82,15 @@ impl Goal for Rc<dyn Goal> {
         self.as_ref().apply(state)
     }
 }
+
+impl<G: Goal> Goal for Rc<G> {
+    fn apply(&self, state: State) -> Option<State> {
+        self.as_ref().apply(state)
+    }
+}
+
+impl<G: Goal> Goal for Box<G> {
+    fn apply(&self, state: State) -> Option<State> {
+        self.as_ref().apply(state)
+    }
+}

canrun/src/goals/not.rs

@@ -12,11 +12,11 @@ A [Goal](crate::goals::Goal) that only succeeds if the sub-goal is proved to alw
 See [`not()`] for more details.
 */
 #[derive(Debug)]
-pub enum Not {
+pub enum Not<G: Goal> {
     /// A `Not` with a sub-goal that failed quickly at creation time
     Fail,
     /// A `Not` goal that needs further evaluation to see if it will succeed.
-    Maybe(Rc<NotConstraint>),
+    Maybe(Rc<NotConstraint<G>>),
 }
 
 /**
@@ -61,7 +61,7 @@ is able to conclusively prove or disprove the sub-goal.
 All of this is not to discourage usage, but just to say that you should try to keep them
 relatively simple and as precise as possible.
 */
-pub fn not(goal: impl Goal) -> Not {
+pub fn not<G: Goal>(goal: G) -> Not<G> {
     // We run the subgoal in isolation right up front for two reasons...
     let mut inner_states = goal.apply(State::new()).into_states().peekable();
     if inner_states.peek().is_none() {
@@ -81,7 +81,7 @@ pub fn not(goal: impl Goal) -> Not {
     }
 }
 
-impl Goal for Not {
+impl<G: Goal> Goal for Not<G> {
     fn apply(&self, state: State) -> Option<State> {
         match self {
             Not::Fail => Some(state),
@@ -96,18 +96,19 @@ impl Goal for Not {
     }
 }
 
-/** A [`Not`] goal that needs to keep evaluating the state as variables are resolved. */
+/** A [`Not`] goal that needs to keep evaluating the state as variables are
+ * resolved. */
 #[derive(Debug)]
-pub struct NotConstraint {
-    goal: Rc<dyn Goal>,
+pub struct NotConstraint<G: Goal> {
+    goal: Rc<G>,
     vars: LVarList,
 }
 
 fn any_succeed(state: Option<State>) -> bool {
     state.into_states().next().is_some()
 }
 
-impl Constraint for NotConstraint {
+impl<G: Goal> Constraint for NotConstraint<G> {
     fn attempt(&self, state: &State) -> Result<ResolveFn, LVarList> {
         // If the internal goal succeeded...
         if any_succeed(self.goal.apply(state.clone())) {

examples/Cargo.toml

@@ -7,7 +7,7 @@ repository = "https://github.com/tgecho/canrun_rs"
 documentation = "https://docs.rs/crate/canrun_collections"
 license = "MIT/Apache-2.0"
 edition = "2021"
-rust-version = "1.70.0"
+rust-version = "1.75.0"
 
 [dependencies]
 canrun = { path = "../canrun"}