Part 1: Parse functions in where clauses.

query-parser/src/parse.rs

@@ -38,6 +38,7 @@ use self::mentat_parser_utils::value_and_span::{
 };
 
 use self::mentat_query::{
+    Binding,
     Direction,
     Element,
     FindQuery,
@@ -57,7 +58,9 @@ use self::mentat_query::{
     SrcVar,
     UnifyVars,
     Variable,
+    VariableOrPlaceholder,
     WhereClause,
+    WhereFn,
 };
 
 error_chain! {
@@ -279,6 +282,25 @@ def_parser!(Where, pred, WhereClause, {
                 })))
 });
 
+/// A vector containing a parenthesized function expression and a binding.
+def_parser!(Where, where_fn, WhereClause, {
+    // Accept either a nested list or a nested vector here:
+    // `[(foo ?x ?y) binding]` or `[[foo ?x ?y] binding]`
+    vector()
+        .of_exactly(
+            (seq().of_exactly(
+                (Query::predicate_fn(), Query::arguments())),
+             Bind::binding())
+                    .map(|((f, args), binding)| {
+                        WhereClause::WhereFn(
+                            WhereFn {
+                                operator: f.0,
+                                args: args,
+                                binding: binding,
+                            })
+                    }))
+});
+
 def_parser!(Where, pattern, WhereClause, {
     vector()
         .of_exactly(
@@ -331,6 +353,7 @@ def_parser!(Where, clause, WhereClause, {
             try(Where::not_clause()),
 
             try(Where::pred()),
+            try(Where::where_fn()),
     ])
 });
 
@@ -345,6 +368,8 @@ def_matches_plain_symbol!(Find, period, ".");
 
 def_matches_plain_symbol!(Find, ellipsis, "...");
 
+def_matches_plain_symbol!(Find, placeholder, "_");
+
 def_parser!(Find, find_scalar, FindSpec, {
     Query::variable()
         .skip(Find::period())
@@ -448,6 +473,48 @@ def_parser!(Find, query, FindQuery, {
         })
 });
 
+pub struct Bind<'a>(std::marker::PhantomData<&'a ()>);
+
+def_parser!(Bind, bind_scalar, Binding, {
+    Query::variable()
+        .skip(eof())
+        .map(|var| Binding::BindScalar(var))
+});
+
+def_parser!(Bind, variable_or_placeholder, VariableOrPlaceholder, {
+    Query::variable().map(VariableOrPlaceholder::Variable)
+        .or(Find::placeholder().map(|_| VariableOrPlaceholder::Placeholder))
+});
+
+def_parser!(Bind, bind_coll, Binding, {
+    vector()
+        .of_exactly(Query::variable()
+            .skip(Find::ellipsis()))
+            .map(Binding::BindColl)
+});
+
+def_parser!(Bind, bind_rel, Binding, {
+    vector().of_exactly(
+        vector().of_exactly(
+            many1::<Vec<VariableOrPlaceholder>, _>(Bind::variable_or_placeholder())
+                .map(Binding::BindRel)))
+});
+
+def_parser!(Bind, bind_tuple, Binding, {
+    vector().of_exactly(
+        many1::<Vec<VariableOrPlaceholder>, _>(Bind::variable_or_placeholder())
+            .map(Binding::BindTuple))
+});
+
+def_parser!(Bind, binding, Binding, {
+    // Any one of the four binding types might apply, so we combine them with `choice`.  Our parsers
+    // consume input, so we need to wrap them in `try` so that they operate independently.
+    choice([try(Bind::bind_scalar()),
+            try(Bind::bind_coll()),
+            try(Bind::bind_tuple()),
+            try(Bind::bind_rel())])
+});
+
 pub fn parse_find_string(string: &str) -> Result<FindQuery> {
     let expr = edn::parse::value(string)?;
     Find::query()
@@ -467,6 +534,7 @@ mod test {
     use self::combine::Parser;
     use self::edn::OrderedFloat;
     use self::mentat_query::{
+        Binding,
         Element,
         FindSpec,
         NonIntegerConstant,
@@ -475,6 +543,7 @@ mod test {
         PatternValuePlace,
         SrcVar,
         Variable,
+        VariableOrPlaceholder,
     };
 
     use super::*;
@@ -793,4 +862,86 @@ mod test {
                                              FnArg::Variable(variable(vy)),
                           ]));
     }
+
+    #[test]
+    fn test_bind_scalar() {
+        let vx = edn::PlainSymbol::new("?x");
+        assert_edn_parses_to!(|| list().of_exactly(Bind::binding()),
+                              "(?x)",
+                              Binding::BindScalar(variable(vx)));
+    }
+
+    #[test]
+    fn test_bind_coll() {
+        let vx = edn::PlainSymbol::new("?x");
+        assert_edn_parses_to!(|| list().of_exactly(Bind::binding()),
+                              "([?x ...])",
+                              Binding::BindColl(variable(vx)));
+    }
+
+    #[test]
+    fn test_bind_rel() {
+        let vx = edn::PlainSymbol::new("?x");
+        let vy = edn::PlainSymbol::new("?y");
+        let vw = edn::PlainSymbol::new("?w");
+        assert_edn_parses_to!(|| list().of_exactly(Bind::binding()),
+                              "([[?x ?y _ ?w]])",
+                              Binding::BindRel(vec![VariableOrPlaceholder::Variable(variable(vx)),
+                                                    VariableOrPlaceholder::Variable(variable(vy)),
+                                                    VariableOrPlaceholder::Placeholder,
+                                                    VariableOrPlaceholder::Variable(variable(vw)),
+                              ]));
+    }
+
+    #[test]
+    fn test_bind_tuple() {
+        let vx = edn::PlainSymbol::new("?x");
+        let vy = edn::PlainSymbol::new("?y");
+        let vw = edn::PlainSymbol::new("?w");
+        assert_edn_parses_to!(|| list().of_exactly(Bind::binding()),
+                              "([?x ?y _ ?w])",
+                              Binding::BindTuple(vec![VariableOrPlaceholder::Variable(variable(vx)),
+                                                      VariableOrPlaceholder::Variable(variable(vy)),
+                                                      VariableOrPlaceholder::Placeholder,
+                                                      VariableOrPlaceholder::Variable(variable(vw)),
+                              ]));
+    }
+
+    #[test]
+    fn test_where_fn() {
+        assert_edn_parses_to!(Where::where_fn,
+                              "[(f ?x 1) ?y]",
+                              WhereClause::WhereFn(WhereFn {
+                                  operator: edn::PlainSymbol::new("f"),
+                                  args: vec![FnArg::Variable(Variable::from_valid_name("?x")),
+                                             FnArg::EntidOrInteger(1)],
+                                  binding: Binding::BindScalar(Variable::from_valid_name("?y")),
+                              }));
+
+        assert_edn_parses_to!(Where::where_fn,
+                              "[(f ?x) [?y ...]]",
+                              WhereClause::WhereFn(WhereFn {
+                                  operator: edn::PlainSymbol::new("f"),
+                                  args: vec![FnArg::Variable(Variable::from_valid_name("?x"))],
+                                  binding: Binding::BindColl(Variable::from_valid_name("?y")),
+                              }));
+
+        assert_edn_parses_to!(Where::where_fn,
+                              "[(f) [?y _]]",
+                              WhereClause::WhereFn(WhereFn {
+                                  operator: edn::PlainSymbol::new("f"),
+                                  args: vec![],
+                                  binding: Binding::BindTuple(vec![VariableOrPlaceholder::Variable(Variable::from_valid_name("?y")),
+                                                                   VariableOrPlaceholder::Placeholder]),
+                              }));
+
+        assert_edn_parses_to!(Where::where_fn,
+                              "[(f) [[_ ?y]]]",
+                              WhereClause::WhereFn(WhereFn {
+                                  operator: edn::PlainSymbol::new("f"),
+                                  args: vec![],
+                                  binding: Binding::BindRel(vec![VariableOrPlaceholder::Placeholder,
+                                                                 VariableOrPlaceholder::Variable(Variable::from_valid_name("?y"))]),
+                              }));
+    }
 }

query/src/lib.rs

@@ -534,6 +534,25 @@ impl FindSpec {
     }
 }
 
+// Datomic accepts variable or placeholder.  DataScript accepts recursive bindings.  Mentat sticks
+// to the non-recursive form Datomic accepts, which is much simpler to process.
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub enum VariableOrPlaceholder {
+    Placeholder,
+    Variable(Variable),
+}
+
+#[derive(Clone,Debug,Eq,PartialEq)]
+pub enum Binding {
+    BindRel(Vec<VariableOrPlaceholder>),
+
+    BindColl(Variable),
+
+    BindTuple(Vec<VariableOrPlaceholder>),
+
+    BindScalar(Variable),
+}
+
 // Note that the "implicit blank" rule applies.
 // A pattern with a reversed attribute — :foo/_bar — is reversed
 // at the point of parsing. These `Pattern` instances only represent
@@ -589,6 +608,13 @@ pub struct Predicate {
     pub args: Vec<FnArg>,
 }
 
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct WhereFn {
+    pub operator: PlainSymbol,
+    pub args: Vec<FnArg>,
+    pub binding: Binding,
+}
+
 #[derive(Clone, Debug, Eq, PartialEq)]
 pub enum UnifyVars {
     /// `Implicit` means the variables in an `or` or `not` are derived from the enclosed pattern.
@@ -664,7 +690,7 @@ pub enum WhereClause {
     NotJoin(NotJoin),
     OrJoin(OrJoin),
     Pred(Predicate),
-    WhereFn,
+    WhereFn(WhereFn),
     RuleExpr,
     Pattern(Pattern),
 }
@@ -730,7 +756,7 @@ impl ContainsVariables for WhereClause {
             &Pred(ref p)    => p.accumulate_mentioned_variables(acc),
             &Pattern(ref p) => p.accumulate_mentioned_variables(acc),
             &NotJoin(ref n) => n.accumulate_mentioned_variables(acc),
-            &WhereFn        => (),
+            &WhereFn(ref f) => f.accumulate_mentioned_variables(acc),
             &RuleExpr       => (),
         }
     }
@@ -794,6 +820,34 @@ impl ContainsVariables for Predicate {
     }
 }
 
+impl ContainsVariables for Binding {
+    fn accumulate_mentioned_variables(&self, acc: &mut BTreeSet<Variable>) {
+        match self {
+            &Binding::BindScalar(ref v) | &Binding::BindColl(ref v) => {
+                acc_ref(acc, v)
+            },
+            &Binding::BindRel(ref vs) | &Binding::BindTuple(ref vs) => {
+                for v in vs {
+                    if let &VariableOrPlaceholder::Variable(ref v) = v {
+                        acc_ref(acc, v);
+                    }
+                }
+            },
+        }
+    }
+}
+
+impl ContainsVariables for WhereFn {
+    fn accumulate_mentioned_variables(&self, acc: &mut BTreeSet<Variable>) {
+        for arg in &self.args {
+            if let &FnArg::Variable(ref v) = arg {
+                acc_ref(acc, v)
+            }
+        }
+        self.binding.accumulate_mentioned_variables(acc);
+    }
+}
+
 fn acc_ref<T: Clone + Ord>(acc: &mut BTreeSet<T>, v: &T) {
     // Roll on, reference entries!
     if !acc.contains(v) {