Feature/552 eval constant terms (#564)

Adds the function `reduce` to all `Terms` in the rule model, which
simplifies constant expressions within `Operation`s

nemo-physical/src/function.rs

@@ -1,7 +1,7 @@
 //! This module contains data structures and implementations
 //! for realizing the evaluation of functions on columnar data.
 
+pub mod evaluation;
 pub mod tree;
 
 pub(crate) mod definitions;
-pub(crate) mod evaluation;

nemo-physical/src/function/evaluation.rs

@@ -52,7 +52,7 @@ pub(crate) enum StackOperation {
 
 /// Representation of a [FunctionTree] as a stack program
 #[derive(Debug, Clone)]
-pub(crate) struct StackProgram {
+pub struct StackProgram {
     /// Maximmum size of the stack
     size: usize,
     /// List of instructions
@@ -115,7 +115,7 @@ impl StackProgram {
     }
 
     /// Construct a [StackProgram] from [FunctionTree].
-    pub(crate) fn from_function_tree<ReferenceType: Hash + Eq + Debug + Clone>(
+    pub fn from_function_tree<ReferenceType: Hash + Eq + Debug + Clone>(
         tree: &FunctionTree<ReferenceType>,
         reference_map: &HashMap<ReferenceType, usize>,
         this: Option<ReferenceType>,
@@ -263,7 +263,7 @@ impl StackProgram {
     ///
     /// # Panics
     /// Panics if the [StackProgram] is not valid.
-    pub(crate) fn evaluate_data(&self, referenced_values: &[AnyDataValue]) -> Option<AnyDataValue> {
+    pub fn evaluate_data(&self, referenced_values: &[AnyDataValue]) -> Option<AnyDataValue> {
         self.evaluate(referenced_values, None)
     }
 
@@ -274,7 +274,7 @@ impl StackProgram {
     ///
     /// # Panics
     /// Panics if the [StackProgram] is not valid.
-    pub(crate) fn evaluate_bool(
+    pub fn evaluate_bool(
         &self,
         referenced_values: &[AnyDataValue],
         this: Option<AnyDataValue>,

nemo-python/src/lib.rs

@@ -13,7 +13,7 @@ use nemo::{
     rule_model::{
         components::{fact::Fact, tag::Tag, term::primitive::Primitive, ProgramComponent},
         error::ValidationErrorBuilder,
-        term_map::PrimitiveTermMap,
+        substitution::Substitution,
     },
 };
 
@@ -269,7 +269,7 @@ impl NemoTrace {
     }
 }
 
-fn assignement_to_dict(assignment: &PrimitiveTermMap, py: Python) -> PyResult<PyObject> {
+fn assignement_to_dict(assignment: &Substitution, py: Python) -> PyResult<PyObject> {
     let dict = PyDict::new_bound(py);
     for (variable, term) in assignment {
         if let Primitive::Ground(ground) = term {

nemo/src/execution/execution_engine.rs

@@ -28,7 +28,7 @@ use crate::{
             term::primitive::{ground::GroundTerm, variable::Variable, Primitive},
         },
         program::Program,
-        term_map::PrimitiveTermMap,
+        substitution::Substitution,
     },
     table_manager::{MemoryUsage, SubtableExecutionPlan, TableManager},
 };
@@ -452,9 +452,9 @@ impl<Strategy: RuleSelectionStrategy> ExecutionEngine<Strategy> {
 
                 let rule_application = TraceRuleApplication::new(
                     rule_index,
-                    PrimitiveTermMap::new(variable_assignment.into_iter().map(
-                        |(variable, value)| (Primitive::from(variable), Primitive::from(value)),
-                    )),
+                    Substitution::new(variable_assignment.into_iter().map(|(variable, value)| {
+                        (Primitive::from(variable), Primitive::from(value))
+                    })),
                     head_index,
                 );
 

nemo/src/execution/planning/operations.rs

@@ -7,5 +7,5 @@ pub(crate) mod filter;
 pub(crate) mod functions;
 pub(crate) mod join;
 pub(crate) mod negation;
-pub(super) mod operation;
+pub(crate) mod operation;
 pub(crate) mod union;

nemo/src/execution/planning/operations/operation.rs

@@ -11,7 +11,7 @@ use crate::{
 };
 
 /// Helper function to translate a [OperationTerm] into a [FunctionTree].
-pub(super) fn operation_term_to_function_tree(
+pub(crate) fn operation_term_to_function_tree(
     translation: &VariableTranslation,
     operation_term: &OperationTerm,
 ) -> FunctionTree<OperationColumnMarker> {
@@ -56,7 +56,7 @@ macro_rules! unary {
 }
 
 /// Helper function to translate a [Operation] into a [FunctionTree].
-pub(super) fn operation_to_function_tree(
+pub(crate) fn operation_to_function_tree(
     translation: &VariableTranslation,
     operation: &Operation,
 ) -> FunctionTree<OperationColumnMarker> {

nemo/src/execution/tracing/trace.rs

@@ -15,7 +15,7 @@ use crate::{
     rule_model::{
         components::{fact::Fact, rule::Rule},
         program::Program,
-        term_map::PrimitiveTermMap,
+        substitution::Substitution,
     },
 };
 
@@ -49,14 +49,14 @@ pub(crate) struct TraceRuleApplication {
     /// Index of the rule that was applied
     rule_index: RuleIndex,
     /// Variable assignment used during the rule application
-    assignment: PrimitiveTermMap,
+    assignment: Substitution,
     /// Index of the head atom which produced the fact under consideration
     _position: usize,
 }
 
 impl TraceRuleApplication {
     /// Create new [TraceRuleApplication].
-    pub fn new(rule_index: RuleIndex, assignment: PrimitiveTermMap, _position: usize) -> Self {
+    pub fn new(rule_index: RuleIndex, assignment: Substitution, _position: usize) -> Self {
         Self {
             rule_index,
             assignment,
@@ -201,7 +201,7 @@ pub struct TraceTreeRuleApplication {
     /// Rule that was applied
     pub rule: Rule,
     /// Variable assignment used during the rule application
-    pub assignment: PrimitiveTermMap,
+    pub assignment: Substitution,
     /// Index of the head atom which produced the fact under consideration
     _position: usize,
 }
@@ -562,7 +562,7 @@ mod test {
                 ProgramComponent,
             },
             program::ProgramBuilder,
-            term_map::PrimitiveTermMap,
+            substitution::Substitution,
         },
     };
 
@@ -579,7 +579,7 @@ mod test {
                 )
             });
 
-            PrimitiveTermMap::new(terms)
+            Substitution::new(terms)
         }};
     }
 

nemo/src/rule_model.rs

@@ -7,5 +7,5 @@ pub mod components;
 pub mod error;
 pub mod origin;
 pub mod program;
-pub mod term_map;
+pub mod substitution;
 pub mod translation;

nemo/src/rule_model/components/parse.rs

@@ -23,35 +23,41 @@ impl Display for ComponentParseError {
 
 #[macro_export]
 macro_rules! parse_component {
-    ($string:expr, $parser:expr, $builder:expr) => {{
-        use nom::InputLength;
-
-        let input = $crate::parser::input::ParserInput::new(
-            $string,
-            $crate::parser::ParserState::default(),
-        );
-        let ast = match $parser(input) {
-            Ok((input, ast)) => {
-                if input.input_len() == 0 {
-                    ast
-                } else {
-                    return Err(
+    ($string:expr, $parser:expr, $builder:expr) => {
+        'parse: {
+            use nom::InputLength;
+
+            let input = $crate::parser::input::ParserInput::new(
+                $string,
+                $crate::parser::ParserState::default(),
+            );
+            let ast = match $parser(input) {
+                Ok((input, ast)) => {
+                    if input.input_len() == 0 {
+                        ast
+                    } else {
+                        break 'parse Err(
+                            $crate::rule_model::components::parse::ComponentParseError::ParseError,
+                        );
+                    }
+                }
+                Err(_) => {
+                    break 'parse Err(
                         $crate::rule_model::components::parse::ComponentParseError::ParseError,
-                    );
+                    )
                 }
-            }
-            Err(_) => {
-                return Err($crate::rule_model::components::parse::ComponentParseError::ParseError)
-            }
-        };
+            };
 
-        let mut translation = ASTProgramTranslation::initialize($string, String::default());
+            let mut translation = ASTProgramTranslation::initialize($string, String::default());
 
-        match $builder(&mut translation, &ast) {
-            Ok(component) => Ok(component),
-            Err(error) => Err(
-                $crate::rule_model::components::parse::ComponentParseError::TranslationError(error),
-            ),
+            match $builder(&mut translation, &ast) {
+                Ok(component) => Ok(component),
+                Err(error) => Err(
+                    $crate::rule_model::components::parse::ComponentParseError::TranslationError(
+                        error,
+                    ),
+                ),
+            }
         }
-    }};
+    };
 }

nemo/src/rule_model/components/tag.rs

@@ -40,6 +40,11 @@ impl Tag {
         self.origin = origin;
         self
     }
+
+    /// Return the name of [Tag].
+    pub fn name(&self) -> &str {
+        &self.tag
+    }
 }
 
 impl Display for Tag {

nemo/src/rule_model/components/term.rs

@@ -31,9 +31,16 @@ use tuple::Tuple;
 use value_type::ValueType;
 
 use crate::{
+    chase_model::translation::ProgramChaseTranslation,
+    execution::{
+        planning::operations::operation::operation_term_to_function_tree,
+        rule_execution::VariableTranslation,
+    },
     parse_component,
+    parser::ast::ProgramAST,
     rule_model::{
-        error::ValidationErrorBuilder, origin::Origin, translation::ASTProgramTranslation,
+        error::ValidationErrorBuilder, origin::Origin, substitution::Substitution,
+        translation::ASTProgramTranslation,
     },
 };
 
@@ -132,6 +139,43 @@ impl Term {
             Term::Tuple(term) => Box::new(term.arguments()),
         }
     }
+
+    /// Return whether this term is ground,
+    /// i.e. whether it does not contain any variables.
+    pub fn is_ground(&self) -> bool {
+        match self {
+            Term::Primitive(term) => term.is_ground(),
+            Term::Aggregate(term) => term.is_ground(),
+            Term::FunctionTerm(term) => term.is_gound(),
+            Term::Map(term) => term.is_gound(),
+            Term::Operation(term) => term.is_gound(),
+            Term::Tuple(term) => term.is_gound(),
+        }
+    }
+
+    /// Reduce (potential) constant expressions contained and return a copy of the resulting [Term].
+    pub fn reduce(&self) -> Term {
+        match self {
+            Term::Operation(operation) => operation.reduce(),
+            Term::Primitive(_) => self.clone(),
+            Term::Aggregate(term) => Term::Aggregate(term.reduce()),
+            Term::FunctionTerm(term) => Term::FunctionTerm(term.reduce()),
+            Term::Map(term) => Term::Map(term.reduce()),
+            Term::Tuple(term) => Term::Tuple(term.reduce()),
+        }
+    }
+
+    /// Reduce (potential) constant expressions
+    /// contained while replacing terms according to the provided substition
+    /// and return a copy of the resulting reduced [Term]
+    pub fn reduce_substitution(&self, substitution: &Substitution) -> Term {
+        // TODO: A more efficient implementation would propagate the substituion
+        // into the subterms and reduce grounded subterms
+        let mut cloned = self.clone();
+        substitution.apply(&mut cloned);
+
+        cloned.reduce()
+    }
 }
 
 impl From<Variable> for Term {
@@ -250,7 +294,7 @@ impl ProgramComponent for Term {
     {
         parse_component!(
             string,
-            crate::parser::ast::expression::Expression::parse_complex,
+            crate::parser::ast::expression::Expression::parse,
             ASTProgramTranslation::build_inner_term
         )
     }
@@ -353,3 +397,32 @@ impl IterablePrimitives for Term {
         }
     }
 }
+
+#[cfg(test)]
+mod test {
+    use crate::rule_model::components::ProgramComponent;
+
+    use super::Term;
+
+    #[test]
+    fn term_reduce_ground() {
+        let constant = Term::parse("2 * (3 + 7)").unwrap();
+        let term = Term::from(tuple!(5, constant));
+
+        let reduced = term.reduce();
+        let expected_term = Term::from(tuple!(5, 20));
+
+        assert_eq!(reduced, expected_term);
+    }
+
+    #[test]
+    fn term_reduce_nonground() {
+        let expression = Term::parse("?x * (3 + 7)").unwrap();
+        let term = Term::from(tuple!(5, expression));
+
+        let reduced = term.reduce();
+        let expected_term = Term::parse("(5, ?x * 10)").unwrap();
+
+        assert_eq!(reduced, expected_term);
+    }
+}