add support for conjunctive queries.

src/prolog/allocator.rs

@@ -0,0 +1,58 @@
+use prolog::ast::*;
+use prolog::fixtures::*;
+use prolog::targets::*;
+
+use std::cell::Cell;
+
+pub trait Allocator<'a>
+{
+    fn new() -> Self;
+    
+    fn mark_anon_var<Target>(&mut self, Level, &mut Vec<Target>)
+        where Target: CompilationTarget<'a>;
+    fn mark_non_var<Target>(&mut self, Level, GenContext, &'a Cell<RegType>, &mut Vec<Target>)
+        where Target: CompilationTarget<'a>;
+    fn mark_var<Target>(&mut self, &'a Var, Level, &'a Cell<VarReg>, GenContext, &mut Vec<Target>)
+        where Target: CompilationTarget<'a>;    
+    
+    fn reset(&mut self);
+    fn reset_contents(&mut self) {}
+
+    fn advance(&mut self, GenContext, &'a Term);
+    fn advance_arg(&mut self);
+
+    fn bindings(&self) -> &AllocVarDict<'a>;
+    fn bindings_mut(&mut self) -> &mut AllocVarDict<'a>;
+
+    fn take_bindings(self) -> AllocVarDict<'a>;
+    
+    fn drain_var_data(&mut self, vs: VariableFixtures<'a>) -> VariableFixtures<'a>
+    {
+        let mut perm_vs = VariableFixtures::new();
+
+        for (var, (var_status, cells)) in vs.into_iter() {
+            match var_status {
+                VarStatus::Temp(chunk_num, tvd) => {
+                    self.bindings_mut().insert(var, VarData::Temp(chunk_num, 0, tvd));
+                },
+                VarStatus::Perm(_) => {
+                    self.bindings_mut().insert(var, VarData::Perm(0));
+                    perm_vs.insert(var, (var_status, cells));
+                }
+            };
+        }
+
+        perm_vs
+    }
+    
+    fn get(&self, var: &'a Var) -> RegType {
+        self.bindings().get(var).unwrap().as_reg_type()
+    }    
+    
+    fn record_register(&mut self, var: &'a Var, r: RegType) {
+        match self.bindings_mut().get_mut(var).unwrap() {
+            &mut VarData::Temp(_, ref mut s, _) => *s = r.reg_num(),
+            &mut VarData::Perm(ref mut s) => *s = r.reg_num()
+        }
+    }
+}