More Datalog

1 files changed, 163 insertions, 0 deletions

diff --git a/crates/elfmind/src/knowledge/relation.rs b/crates/elfmind/src/knowledge/relation.rs
new file mode 100644
index 0000000..754bf0f
--- /dev/null
+++ b/crates/elfmind/src/knowledge/relation.rs
@@ -0,0 +1,163 @@
+use super::{Value, Hole, Unification};
+
+use crate::time::*;
+use crate::item::*;
+use crate::character::*;
+
+use enum_map::Enum;
+use strum::EnumDiscriminants;
+
+pub trait Substitutable {
+    fn substitute(&self, u: &Unification) -> Self;
+}
+impl<A: Clone + TryFrom<Value>> Substitutable for Hole<A> {
+    fn substitute(&self, u: &Unification) -> Self {
+        match self {
+            x@Self::Var(v) => if let Some(y) = u.lookup(v) && let Ok(z) = A::try_from(y) {
+                Hole::Val(z)
+            } else {
+                x.clone()
+            }
+            x => x.clone(),
+        }
+    }
+}
+impl<
+    A: Clone + TryFrom<Value>,
+    B: Clone + TryFrom<Value>
+    > Substitutable for (Hole<A>, Hole<B>) {
+    fn substitute(&self, u: &Unification) -> Self {
+        let (a, b) = self;
+        (a.substitute(u), b.substitute(u))
+    }
+}
+impl<
+    A: Clone + TryFrom<Value>,
+    B: Clone + TryFrom<Value>,
+    C: Clone + TryFrom<Value>,
+    > Substitutable for (Hole<A>, Hole<B>, Hole<C>) {
+    fn substitute(&self, u: &Unification) -> Self {
+        let (a, b, c) = self;
+        (a.substitute(u), b.substitute(u), c.substitute(u))
+    }
+}
+impl<
+    A: Clone + TryFrom<Value>,
+    B: Clone + TryFrom<Value>,
+    C: Clone + TryFrom<Value>,
+    D: Clone + TryFrom<Value>,
+    > Substitutable for (Hole<A>, Hole<B>, Hole<C>, Hole<D>) {
+    fn substitute(&self, u: &Unification) -> Self {
+        let (a, b, c, d) = self;
+        (a.substitute(u), b.substitute(u), c.substitute(u), d.substitute(u))
+    }
+}
+impl<
+    A: Clone + TryFrom<Value>,
+    B: Clone + TryFrom<Value>,
+    C: Clone + TryFrom<Value>,
+    D: Clone + TryFrom<Value>,
+    E: Clone + TryFrom<Value>,
+    > Substitutable for (Hole<A>, Hole<B>, Hole<C>, Hole<D>, Hole<E>) {
+    fn substitute(&self, u: &Unification) -> Self {
+        let (a, b, c, d, e) = self;
+        (a.substitute(u), b.substitute(u), c.substitute(u), d.substitute(u), e.substitute(u))
+    }
+}
+
+pub trait Unifiable {
+    fn unify(&self, other: &Self, u: Unification) -> Option<Unification>;
+}
+impl<A> Unifiable for Hole<A> where
+    Value: From<A>, A: Copy, 
+{
+    fn unify(&self, other: &Self, mut u: Unification) -> Option<Unification> {
+        if u.unify_hole(self, other) {
+            Some(u)
+        } else { None }
+    }
+}
+impl<A, B> Unifiable for (Hole<A>, Hole<B>) where
+    Value: From<A>, A: Copy, 
+    Value: From<B>, B: Copy,
+{
+    fn unify(&self, other: &Self, mut u: Unification) -> Option<Unification> {
+        let (a1, b1) = self;
+        let (a2, b2) = other;
+        if u.unify_hole(a1, a2) && u.unify_hole(b1, b2) {
+            Some(u)
+        } else { None }
+    }
+}
+impl<A, B, C> Unifiable for (Hole<A>, Hole<B>, Hole<C>) where
+    Value: From<A>, A: Copy, 
+    Value: From<B>, B: Copy,
+    Value: From<C>, C: Copy,
+{
+    fn unify(&self, other: &Self, mut u: Unification) -> Option<Unification> {
+        let (a1, b1, c1) = self;
+        let (a2, b2, c2) = other;
+        if u.unify_hole(a1, a2) && u.unify_hole(b1, b2) && u.unify_hole(c1, c2) {
+            Some(u)
+        } else { None }
+    }
+}
+impl<A, B, C, D> Unifiable for (Hole<A>, Hole<B>, Hole<C>, Hole<D>) where
+    Value: From<A>, A: Copy, 
+    Value: From<B>, B: Copy,
+    Value: From<C>, C: Copy,
+    Value: From<D>, D: Copy,
+{
+    fn unify(&self, other: &Self, mut u: Unification) -> Option<Unification> {
+        let (a1, b1, c1, d1) = self;
+        let (a2, b2, c2, d2) = other;
+        if u.unify_hole(a1, a2) && u.unify_hole(b1, b2) && u.unify_hole(c1, c2) && u.unify_hole(d1, d2) {
+            Some(u)
+        } else { None }
+    }
+}
+impl<A, B, C, D, E> Unifiable for (Hole<A>, Hole<B>, Hole<C>, Hole<D>, Hole<E>) where
+    Value: From<A>, A: Copy, 
+    Value: From<B>, B: Copy,
+    Value: From<C>, C: Copy,
+    Value: From<D>, D: Copy,
+    Value: From<E>, E: Copy,
+{
+    fn unify(&self, other: &Self, mut u: Unification) -> Option<Unification> {
+        let (a1, b1, c1, d1, e1) = self;
+        let (a2, b2, c2, d2, e2) = other;
+        if u.unify_hole(a1, a2) && u.unify_hole(b1, b2) && u.unify_hole(c1, c2) && u.unify_hole(d1, d2) && u.unify_hole(e1, e2) {
+            Some(u)
+        } else { None }
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash, EnumDiscriminants)]
+#[strum_discriminants(derive(Enum))]
+pub enum Relation {
+    HasItem((Hole<Character>, Hole<Item>)),
+    UsedItemAt((Hole<Character>, Hole<Item>, Hole<Time>)),
+    TimeIs(Hole<Time>),
+    FriendOf((Hole<Character>, Hole<Character>)),
+}
+impl Substitutable for Relation {
+    fn substitute(&self, u: &Unification) -> Self {
+        match self {
+            Self::HasItem(x) => Self::HasItem(x.substitute(u)),
+            Self::UsedItemAt(x) => Self::UsedItemAt(x.substitute(u)),
+            Self::TimeIs(x) => Self::TimeIs(x.substitute(u)),
+            Self::FriendOf(x) => Self::FriendOf(x.substitute(u)),
+        }
+    }
+}
+impl Unifiable for Relation {
+    fn unify(&self, other: &Self, u: Unification) -> Option<Unification> {
+        match (self, other) {
+            (Self::HasItem(a), Self::HasItem(b)) => a.unify(b, u),
+            (Self::UsedItemAt(a), Self::UsedItemAt(b)) => a.unify(b, u),
+            (Self::TimeIs(a), Self::TimeIs(b)) => a.unify(b, u),
+            (Self::FriendOf(a), Self::FriendOf(b)) => a.unify(b, u),
+            _ => None,
+        }
+    }
+}