evaluate expressions

src/data/expr.rs

@@ -4,21 +4,48 @@ use anyhow::Result;
 use itertools::Itertools;
 
 use crate::data::expr::ExprError::UnexpectedArgs;
+use crate::data::keyword::Keyword;
+use crate::data::tuple::Tuple;
 use crate::data::value::DataValue;
-use crate::query::compile::Term;
 
 #[derive(Debug, thiserror::Error)]
 pub enum ExprError {
     #[error("unexpected args for {0}: {1:?}")]
     UnexpectedArgs(&'static str, Vec<DataValue>),
+    #[error("unexpected return type: expected {0}, got {1:?}")]
+    UnexpectedReturnType(String, DataValue),
 }
 
 #[derive(Debug, Clone)]
 pub enum Expr {
-    Const(Term<DataValue>),
+    Binding(Keyword),
+    BoundIdx(usize),
+    Const(DataValue),
     Apply(&'static Op, Box<[Expr]>),
 }
 
+impl Expr {
+    pub(crate) fn eval(&self, bindings: &Tuple) -> Result<DataValue> {
+        match self {
+            Expr::Binding(_) => {
+                unreachable!()
+            }
+            Expr::BoundIdx(i) => Ok(bindings.0[*i].clone()),
+            Expr::Const(d) => Ok(d.clone()),
+            Expr::Apply(op, args) => {
+                let args: Box<[DataValue]> = args.iter().map(|v| v.eval(bindings)).try_collect()?;
+                (op.inner)(&args)
+            }
+        }
+    }
+    pub(crate) fn eval_pred(&self, bindings: &Tuple) -> Result<bool> {
+        match self.eval(bindings)? {
+            DataValue::Bool(b) => Ok(b),
+            v => Err(ExprError::UnexpectedReturnType("bool".to_string(), v).into()),
+        }
+    }
+}
+
 #[derive(Clone)]
 pub struct Op {
     pub(crate) name: &'static str,
@@ -171,4 +198,4 @@ fn op_not(args: &[DataValue]) -> Result<DataValue> {
     } else {
         Err(UnexpectedArgs("not", args.to_vec()).into())
     }
-}
+}

src/parse/query.rs

@@ -7,7 +7,8 @@ use serde_json::Map;
 
 use crate::data::attr::Attribute;
 use crate::data::expr::{
-    Expr, OP_ADD, OP_DIV, OP_EQ, OP_GE, OP_GT, OP_LE, OP_LT, OP_MUL, OP_NEQ, OP_SUB,
+    Expr, OP_ADD, OP_AND, OP_DIV, OP_EQ, OP_GE, OP_GT, OP_LE, OP_LT, OP_MUL, OP_NEQ, OP_NOT, OP_OR,
+    OP_SUB,
 };
 use crate::data::json::JsonValue;
 use crate::data::keyword::{Keyword, PROG_ENTRY};
@@ -112,6 +113,9 @@ impl SessionTx {
             "Ge" => &OP_GE,
             "Lt" => &OP_LT,
             "Le" => &OP_LE,
+            "Or" => &OP_OR,
+            "And" => &OP_AND,
+            "Not" => &OP_NOT,
             s => return Err(QueryCompilationError::UnknownOperator(s.to_string()).into()),
         };
 
@@ -159,14 +163,14 @@ impl SessionTx {
             JsonValue::String(s) => {
                 let kw = Keyword::from(s as &str);
                 if kw.is_reserved() {
-                    Ok(Expr::Const(Term::Var(kw)))
+                    Ok(Expr::Binding(kw))
                 } else {
-                    Ok(Expr::Const(Term::Const(DataValue::String(s.into()))))
+                    Ok(Expr::Const(DataValue::String(s.into())))
                 }
             }
             JsonValue::Object(map) => {
                 if let Some(v) = map.get("const") {
-                    Ok(Expr::Const(Term::Const(v.into())))
+                    Ok(Expr::Const(v.into()))
                 } else if map.contains_key("pred") {
                     Self::parse_expr(map)
                 } else {
@@ -177,7 +181,7 @@ impl SessionTx {
                     .into())
                 }
             }
-            v => Ok(Expr::Const(Term::Const(v.into()))),
+            v => Ok(Expr::Const(v.into())),
         }
     }
     fn parse_rule_atom(&mut self, payload: &Map<String, JsonValue>, vld: Validity) -> Result<Atom> {