Introduce expressions and computed value variables in typeql-rust (#294)

## What is the goal of this PR?

We introduce in `typeql-rust` the ability to perform arithmetic
computation and store the results in a "value variable" - denoted by a
preceding `?`, the same as introduced in `typeql-java` by
#260.

All redundant parenthesis from original query will not persist in the
string representation of the parsed expression anymore. If we get this
query:
```
match
  $p isa person, has salary $s;
  ?net = (($s - 12500) * 0.8 + 12500);
```
it will be transformed into
```
match
  $p isa person, has salary $s;
  ?net = ($s - 12500) * 0.8 + 12500;
```

## What are the changes implemented in this PR?

In addition to changes implemented in
#260:
- We removed `Parenthesis` class and do not store parenthesis in the
expression tree anymore. When we build a string representation of the
expression, we add all necessary parenthesis. Nevertheless, if we get
something like `a + (b + c)`, these parenthesis will persist in the
resulting string representation.

Author: dmikhalin

grammar/TypeQL.g4

@@ -201,12 +201,10 @@ type                  :   label                         | VAR_CONCEPT_
 
 label_any             :   label_scoped  | label         ;
 label_scoped          :   LABEL_SCOPED_ ;
-label                 :   LABEL_        | schema_native | type_native   | unreserved    ;
+label                 :   LABEL_        | type_native   | unreserved    ;
 
 // LITERAL INPUT VALUES ========================================================
 
-schema_native         :   RULE            ;
-
 type_native           :   THING           |   ENTITY          |   ATTRIBUTE
                       |   RELATION        |   ROLE            ;
 
@@ -226,6 +224,7 @@ sign                  :   ADD             |  SUBTRACT         ;
 unreserved            : VALUE | EXPR_FUNC_NAME
                       | MIN | MAX | MEDIAN | MEAN | STD | SUM | COUNT
                       | GET | SORT | LIMIT | OFFSET | GROUP | CONTAINS
+                      | RULE
                       ;
 
 // TYPEQL SYNTAX KEYWORDS =======================================================
@@ -290,7 +289,7 @@ DIVIDE          : '/'           ;   MULTIPLY        : '*'           ;
 POWER           : '^'           ;   MODULO          : '%'           ;
 PAREN_OPEN      : '('           ;   PAREN_CLOSE     : ')'           ;
 
-// Incomplete list of function names usable in expressions. The 'func_name' rule references all function names.
+// Incomplete list of function names usable in expressions. The 'expression_function_name' rule references all function names.
 EXPR_FUNC_NAME  :  'floor' | 'ceil' | 'round' | 'abs'               ;
 
 // GROUP AND AGGREGATE QUERY KEYWORDS (also used by COMPUTE QUERY)

rust/builder/mod.rs

@@ -21,10 +21,11 @@
  */
 
 use crate::{
-    common::token::Predicate,
+    common::token,
     pattern::{
-        Negation, RelationVariableBuilder, RolePlayerConstraint, RuleDeclaration, ThingVariable, TypeVariable,
-        TypeVariableBuilder, UnboundVariable, Value, ValueConstraint,
+        Constant, Expression, Function, Negation, PredicateConstraint, RelationVariableBuilder, RolePlayerConstraint,
+        RuleDeclaration, ThingVariable, TypeVariable, TypeVariableBuilder, UnboundConceptVariable,
+        UnboundValueVariable, Value,
     },
     Pattern,
 };
@@ -75,6 +76,42 @@ macro_rules! or {
     }}
 }
 
+#[macro_export]
+macro_rules! max {
+    ($($arg:expr),* $(,)?) => {{
+        let args = [$($arg, )*];
+        $crate::pattern::Expression::Function($crate::pattern::Function {
+            function_name: $crate::common::token::Function::Max,
+            args: args.into_iter().map(|arg| Box::new(arg.into())).collect(),
+        })
+    }}
+}
+
+#[macro_export]
+macro_rules! min {
+    ($($arg:expr),* $(,)?) => {{
+        let args = [$($arg, )*];
+        $crate::pattern::Expression::Function($crate::pattern::Function {
+            function_name: token::Function::Min,
+            args: args.into_iter().map(|arg| Box::new(arg.into())).collect(),
+        })
+    }}
+}
+
+#[macro_export]
+macro_rules! filter {
+    ($($arg:expr),* $(,)?) => {{
+        [$(Into::<$crate::pattern::UnboundVariable>::into($arg)),*]
+    }}
+}
+
+#[macro_export]
+macro_rules! sort_vars {
+    ($($arg:expr),*) => {{
+        $crate::query::Sorting::new(vec![$(Into::<$crate::query::sorting::OrderedVariable>::into($arg), )*])
+    }}
+}
+
 pub fn not<T: Into<Pattern>>(pattern: T) -> Negation {
     Negation::new(pattern.into())
 }
@@ -83,46 +120,70 @@ pub fn rule(name: &str) -> RuleDeclaration {
     RuleDeclaration::from(name)
 }
 
-pub fn var(var: impl Into<UnboundVariable>) -> UnboundVariable {
+pub fn cvar(var: impl Into<UnboundConceptVariable>) -> UnboundConceptVariable {
+    var.into()
+}
+
+pub fn vvar(var: impl Into<UnboundValueVariable>) -> UnboundValueVariable {
     var.into()
 }
 
+pub fn constant(constant: impl Into<Constant>) -> Constant {
+    constant.into()
+}
+
 pub fn type_(name: impl Into<String>) -> TypeVariable {
-    UnboundVariable::hidden().type_(name.into())
+    UnboundConceptVariable::hidden().type_(name.into())
 }
 
 pub fn rel<T: Into<RolePlayerConstraint>>(value: T) -> ThingVariable {
-    UnboundVariable::hidden().rel(value)
+    UnboundConceptVariable::hidden().rel(value)
+}
+
+pub fn eq<T: Into<Value>>(value: T) -> PredicateConstraint {
+    PredicateConstraint::new(token::Predicate::Eq, value.into())
+}
+
+pub fn neq<T: Into<Value>>(value: T) -> PredicateConstraint {
+    PredicateConstraint::new(token::Predicate::Neq, value.into())
+}
+
+pub fn lt<T: Into<Value>>(value: T) -> PredicateConstraint {
+    PredicateConstraint::new(token::Predicate::Lt, value.into())
+}
+
+pub fn lte<T: Into<Value>>(value: T) -> PredicateConstraint {
+    PredicateConstraint::new(token::Predicate::Lte, value.into())
 }
 
-pub fn eq<T: Into<Value>>(value: T) -> ValueConstraint {
-    ValueConstraint::new(Predicate::Eq, value.into())
+pub fn gt<T: Into<Value>>(value: T) -> PredicateConstraint {
+    PredicateConstraint::new(token::Predicate::Gt, value.into())
 }
 
-pub fn neq<T: Into<Value>>(value: T) -> ValueConstraint {
-    ValueConstraint::new(Predicate::Neq, value.into())
+pub fn gte<T: Into<Value>>(value: T) -> PredicateConstraint {
+    PredicateConstraint::new(token::Predicate::Gte, value.into())
 }
 
-pub fn lt<T: Into<Value>>(value: T) -> ValueConstraint {
-    ValueConstraint::new(Predicate::Lt, value.into())
+pub fn contains<T: Into<String>>(value: T) -> PredicateConstraint {
+    PredicateConstraint::new(token::Predicate::Contains, Value::from(value.into()))
 }
 
-pub fn lte<T: Into<Value>>(value: T) -> ValueConstraint {
-    ValueConstraint::new(Predicate::Lte, value.into())
+pub fn like<T: Into<String>>(value: T) -> PredicateConstraint {
+    PredicateConstraint::new(token::Predicate::Like, Value::from(value.into()))
 }
 
-pub fn gt<T: Into<Value>>(value: T) -> ValueConstraint {
-    ValueConstraint::new(Predicate::Gt, value.into())
+pub fn abs<T: Into<Expression>>(arg: T) -> Function {
+    Function { function_name: token::Function::Abs, args: vec![Box::from(arg.into())] }
 }
 
-pub fn gte<T: Into<Value>>(value: T) -> ValueConstraint {
-    ValueConstraint::new(Predicate::Gte, value.into())
+pub fn ceil<T: Into<Expression>>(arg: T) -> Function {
+    Function { function_name: token::Function::Ceil, args: vec![Box::from(arg.into())] }
 }
 
-pub fn contains<T: Into<String>>(value: T) -> ValueConstraint {
-    ValueConstraint::new(Predicate::Contains, Value::from(value.into()))
+pub fn floor<T: Into<Expression>>(arg: T) -> Function {
+    Function { function_name: token::Function::Floor, args: vec![Box::from(arg.into())] }
 }
 
-pub fn like<T: Into<String>>(value: T) -> ValueConstraint {
-    ValueConstraint::new(Predicate::Like, Value::from(value.into()))
+pub fn round<T: Into<Expression>>(arg: T) -> Function {
+    Function { function_name: token::Function::Round, args: vec![Box::from(arg.into())] }
 }

rust/common/error/mod.rs

@@ -97,6 +97,8 @@ error_messages! { TypeQLError
         6: "The query has not been provided with any definables.",
     MatchHasNoBoundingNamedVariable() =
         7: "The match query does not have named variables to bound the nested disjunction/negation pattern(s).",
+    VariableNameConflict(String) =
+        8: "The variable names '{}' cannot be used for both concept variables and value variables.",
     MatchPatternVariableHasNoNamedVariable(Pattern) =
         9: "The pattern '{}' has no named variable.",
     MatchHasUnboundedNestedPattern(Pattern) =

rust/common/token.rs

@@ -80,15 +80,16 @@ string_enum! { Filter
     Limit = "limit",
 }
 
-string_enum! { Operator
+string_enum! { LogicOperator
     And = "and",
     Or = "or",
     Not = "not",
 }
 
 string_enum! { Predicate
     // equality
-    Eq = "=",
+    Eq = "==",
+    EqLegacy = "=",   // TODO: Deprecate '=' as equality in 3.0
     Neq = "!=",
     Gt = ">",
     Gte = ">=",
@@ -102,7 +103,7 @@ string_enum! { Predicate
 impl Predicate {
     pub fn is_equality(&self) -> bool {
         use Predicate::*;
-        matches!(self, Eq | Neq | Gt | Gte | Lt | Lte)
+        matches!(self, Eq | EqLegacy | Neq | Gt | Gte | Lt | Lte) // TODO: Deprecate '=' as equality in 3.0
     }
 
     pub fn is_substring(&self) -> bool {
@@ -120,6 +121,7 @@ string_enum! { Schema
 string_enum! { Constraint
     Abstract = "abstract",
     As = "as",
+    Assign = "=",
     Has = "has",
     IID = "iid",
     Is = "is",
@@ -162,3 +164,21 @@ string_enum! { Order
     Asc = "asc",
     Desc = "desc",
 }
+
+string_enum! { ArithmeticOperator
+    Add = "+",
+    Subtract = "-",
+    Multiply = "*",
+    Divide = "/",
+    Modulo = "%",
+    Power = "^",
+}
+
+string_enum! { Function
+    Abs = "abs",
+    Ceil = "ceil",
+    Floor = "floor",
+    Max = "max",
+    Min = "min",
+    Round = "round",
+}