refactors Problem, adds Solution

planner/src/bin/weekly.rs

@@ -5,20 +5,19 @@ extern crate cookbook;
 
 use std::time;
 use std::fmt::Debug;
-use std::fmt::Display;
 use std::hash::Hash;
 use cookbook::*;
 use planner::{
     *, Value,
     solver::{
-        Variables,
+        Solution,
         Domain,
         Problem
     }
 };
 
 
-fn pretty_output<K: Eq + Hash + Debug>(res: &Variables<Value, K>) -> String {
+fn pretty_output<K: Eq + Hash + Debug>(res: &Solution<Value, K>) -> String {
     let mut repr = String::new();
     for (var,value) in res {
         let value = match value {

planner/src/solver.rs

@@ -7,11 +7,13 @@ use std::clone::Clone;
 use std::collections::HashMap;
 
 /// An assignments map of variables
-pub type Variables<'a, V, K> = HashMap<K, Option<&'a V>>;
+type Variables<'a, V> = Vec<Option<&'a V>>;
+/// A solution returned by [`Solver`]
+pub type Solution<'a, V, K> = HashMap<K, Option<&'a V>>;
 
-enum Assignment<'a, V, K> {
-    Update(K, &'a V),
-    Clear(K)
+enum Assignment<'a, V> {
+    Update(usize, &'a V),
+    Clear(usize)
 }
 
 /// Collection of references to values owned by a domain.
@@ -99,7 +101,7 @@ impl<V: fmt::Debug> fmt::Debug for Domain<V> {
 }
 
 
-pub type Constraint<'a,V, K> = fn(&Variables<'a,V, K>) -> bool;
+pub type Constraint<'a,V> = fn(&Variables<'a,V>) -> bool;
 
 
 /// Could be more efficient to just use fixed array of options as variables,
@@ -108,12 +110,13 @@ pub type Constraint<'a,V, K> = fn(&Variables<'a,V, K>) -> bool;
 /// It makes sense with an array where indexing is O(1)
 
 pub struct Problem<'a, V, K> {
+    keys: Vec<K>,
     /// The initial assignements map
-    variables: Variables<'a, V, K>,
+    variables: Variables<'a, V>,
     /// Each variable has its associated domain
-    domains: HashMap<K, DomainValues<'a,V>>,
+    domains: Vec<DomainValues<'a,V>>,
     /// Set of constraints to validate
-    constraints: Vec<Constraint<'a,V,K>>,
+    constraints: Vec<Constraint<'a,V>>,
 }
 
 impl<'a, V, K: Eq + Hash + Clone> Problem<'a, V, K> {
@@ -123,14 +126,14 @@ impl<'a, V, K: Eq + Hash + Clone> Problem<'a, V, K> {
     }
 
     pub fn from_template() -> Problem<'a, V, K> {
-        let mut builder = Self::build();
+        let builder = Self::build();
 
         builder.finish()
     }
 
     /// Returns all possible Updates for next assignements, prepended with
     /// a Clear to ensure the variable is unset before when leaving the branch.
-    fn _push_updates(&self) -> Option<Vec<Assignment<'a,V, K>>> {
+    fn _push_updates(&self) -> Option<Vec<Assignment<'a,V>>> {
         // TODO: should be able to inject a choosing strategy
         if let Some(key) = self._next_assign() {
             let domain_values = self.domains
@@ -142,10 +145,7 @@ impl<'a, V, K: Eq + Hash + Clone> Problem<'a, V, K> {
             // TODO: should be able to filter domain values (inference, pertinence)
             domain_values.iter().for_each(|value| {
                 updates.push(
-                    Assignment::Update(
-                        key.clone(),
-                        *value
-                    )
+                    Assignment::Update(key, *value)
                 );
             });
             Some(updates)
@@ -154,11 +154,11 @@ impl<'a, V, K: Eq + Hash + Clone> Problem<'a, V, K> {
         }
     }
 
-    fn _next_assign(&self) -> Option<&K> {
-        self.variables
-            .iter()
-            .find_map(|(key, val)| {
-                    if val.is_none() { Some(key) }
+    fn _next_assign(&self) -> Option<usize> {
+        self.variables.iter()
+            .enumerate()
+            .find_map(|(idx, val)| {
+                    if val.is_none() { Some(idx) }
                     else { None }
             })
     }
@@ -171,13 +171,9 @@ impl<'a, V, K: Eq + Hash + Clone> Problem<'a, V, K> {
         return true;
     }
 
-    /// Returns all complete solutions, after visiting all possible outcomes using a stack (DFS).
-    pub fn solve_all(&mut self) -> Vec<Variables<'a,V,K>>
-        where V: Clone + fmt::Debug,
-              K: Clone + fmt::Debug,
-    {
-        let mut solutions: Vec<Variables<V, K>> = vec![];
-        let mut stack: Vec<Assignment<'a, V, K>> = vec![];
+    fn _solve(&mut self, limit: Option<usize>) -> Vec<Solution<'a, V, K>> {
+        let mut solutions: Vec<Solution<V, K>> = vec![];
+        let mut stack: Vec<Assignment<'a, V>> = vec![];
         if let Some(mut init_updates) = self._push_updates() {
             stack.append(&mut init_updates);
         } else {
@@ -187,66 +183,56 @@ impl<'a, V, K: Eq + Hash + Clone> Problem<'a, V, K> {
 
         loop {
             let node = stack.pop();
+            // There is no more combination to try out
             if node.is_none() { break; };
+            // Exit early if we have enough solutions
+            if limit.is_some()
+               && solutions.len() == limit.unwrap()
+            {
+                break;
+            };
+
             match node.unwrap() {
-                Assignment::Update(key, val) => {
+                Assignment::Update(idx, val) => {
                     // Assign the variable and open new branches, if any.
-                    *self.variables.get_mut(&key).unwrap() = Some(val);
+                    self.variables[idx] = Some(val);
                     // TODO: handle case of empty domain.values
                     if let Some(mut nodes) = self._push_updates() {
                         stack.append(&mut nodes);
                     } else {
                         // Assignements are completed
                         if self._is_valid() {
-                            solutions.push(self.variables.clone());
+                            solutions.push(
+                                // Builds Solution
+                                self.keys.iter().cloned()
+                                    .zip(self.variables.iter().cloned())
+                                    .collect()
+                            );
                         };
                     };
                 },
-                Assignment::Clear(key) => {
+                Assignment::Clear(idx) => {
                     // We are closing this branch, unset the variable
-                    *self.variables.get_mut(&key).unwrap() = None;
+                    self.variables[idx] = None;
                 },
             };
         };
         solutions
-    }
 
-    pub fn solve_one(&mut self) -> Option<Variables<'a,V,K>>
+    }
+    /// Returns all complete solutions, after visiting all possible outcomes using a stack (DFS).
+    pub fn solve_all(&mut self) -> Vec<Solution<'a,V,K>>
         where V: Clone + fmt::Debug,
               K: Clone + fmt::Debug,
     {
-        let mut stack: Vec<Assignment<'a, V, K>> = vec![];
-        if let Some(mut init_updates) = self._push_updates() {
-            stack.append(&mut init_updates);
-        } else {
-            panic!("Could not initialize !");
+        self._solve(None) // No limit
     }
 
-        loop {
-            let node = stack.pop();
-            if node.is_none() {
-                return None;
-            };
-            match node.unwrap() {
-                Assignment::Update(key, val) => {
-                    // Assign the variable and open new branches, if any.
-                    *self.variables.get_mut(&key).unwrap() = Some(val);
-                    // TODO: handle case of empty domain.values
-                    if let Some(mut nodes) = self._push_updates() {
-                        stack.append(&mut nodes);
-                    } else {
-                        // Assignements are completed
-                        if self._is_valid() {
-                            return Some(self.variables.clone());
-                        };
-                    };
-                },
-                Assignment::Clear(key) => {
-                    // We are closing this branch, unset the variable
-                    *self.variables.get_mut(&key).unwrap() = None;
-                },
-            };
-        }
+    pub fn solve_one(&mut self) -> Option<Solution<'a,V,K>>
+        where V: Clone + fmt::Debug,
+              K: Clone + fmt::Debug,
+    {
+        self._solve(Some(1)).pop()
     }
 }
 
@@ -256,20 +242,22 @@ impl<'a, V, K: Eq + Hash + Clone> ProblemBuilder<'a, V, K> {
     fn new() -> ProblemBuilder<'a, V, K> {
         ProblemBuilder(
             Problem{
+                keys: Vec::new(),
                 variables: Variables::new(),
-                domains: HashMap::new(),
+                domains: Vec::new(),
                 constraints: Vec::new(),
             })
     }
 
     pub fn add_variable(mut self, name: K, domain: Vec<&'a V>, value: Option<&'a V>) -> Self
     {
-        self.0.variables.insert(name.clone(), value);
-        self.0.domains.insert(name, domain);
+        self.0.keys.push(name);
+        self.0.variables.push(value);
+        self.0.domains.push(domain);
         self
     }
 
-    pub fn add_constraint(mut self, cons: Constraint<'a,V, K>) -> Self {
+    pub fn add_constraint(mut self, cons: Constraint<'a,V>) -> Self {
         self.0.constraints.push(cons);
         self
     }
@@ -289,15 +277,15 @@ mod tests {
         let mut problem: Problem<_, _> = Problem::build()
             .add_variable(String::from("Left"), domain.all(), None)
             .add_variable(String::from("Right"), domain.all(), None)
-            .add_constraint(|assign: &Variables<i32, _>| {
-                assign.get("Left").unwrap() == assign.get("Right").unwrap()
+            .add_constraint(|assign: &Variables<i32>| {
+                assign[0] == assign[1]
             })
             .finish();
 
-        let solutions: Vec<Variables<i32, _>> = vec![
-            [("Left".to_string(), Some(&3)), ("Right".to_string(), Some(&3)),].iter().cloned().collect(),
-            [("Left".to_string(), Some(&2)), ("Right".to_string(), Some(&2)),].iter().cloned().collect(),
-            [("Left".to_string(), Some(&1)), ("Right".to_string(), Some(&1)),].iter().cloned().collect(),
+        let solutions: Vec<Solution<i32, _>> = vec![
+            [(String::from("Left"), Some(&3)), (String::from("Right"), Some(&3))].iter().cloned().collect(),
+            [(String::from("Left"), Some(&2)), (String::from("Right"), Some(&2))].iter().cloned().collect(),
+            [(String::from("Left"), Some(&1)), (String::from("Right"), Some(&1))].iter().cloned().collect(),
         ];
 
         assert_eq!(problem.solve_all(), solutions);
@@ -310,13 +298,13 @@ mod tests {
         let mut problem: Problem<_, _> = Problem::build()
             .add_variable("Left".to_string(), domain.all(), None)
             .add_variable("Right".to_string(), domain.all(), Some(&2))
-            .add_constraint( |assign: &Variables<i32, _>| {
-                assign.get("Left").unwrap() == assign.get("Right").unwrap()
+            .add_constraint( |assign: &Variables<i32>| {
+                assign[0] == assign[1]
             })
             .finish();
 
-        let solutions: Vec<Variables<i32, _>> = vec![
-            [("Left".to_string(), Some(&2)), ("Right".to_string(), Some(&2)),].iter().cloned().collect(),
+        let solutions: Vec<Solution<i32, String>> = vec![
+            [(String::from("Left"), Some(&2)), (String::from("Right"), Some(&2))].iter().cloned().collect(),
         ];
 
         assert_eq!(problem.solve_all(), solutions);