Create assignment = built-in operator.

compiler/dialect_libraries/bq_library.py

@@ -16,6 +16,7 @@
 
 library = """
 ->(left:, right:) = {arg: left, value: right};
+`=`(left:, right:) = right :- left == right;
 
 # All ORDER BY arguments are wrapped, to avoid confusion with
 # column index.

compiler/dialect_libraries/presto_library.py

@@ -16,6 +16,7 @@
 
 library = """
 ->(left:, right:) = {arg: left, value: right};
+`=`(left:, right:) = right :- left == right;
 
 ArgMin(a) = SqlExpr("(ARRAY_AGG({arg} order by {value}))[1]",
                     {arg: a.arg, value: a.value});

compiler/dialect_libraries/psql_library.py

@@ -16,6 +16,7 @@
 
 library = """
 ->(left:, right:) = {arg: left, value: right};
+`=`(left:, right:) = right :- left == right;
 
 ArgMin(a) = SqlExpr("(ARRAY_AGG({arg} order by {value}))[1]",
                     {arg: a.arg, value: a.value});

compiler/dialect_libraries/sqlite_library.py

@@ -16,6 +16,7 @@
 
 library = """
 ->(left:, right:) = {arg: left, value: right};
+`=`(left:, right:) = right :- left == right;
 
 Arrow(left, right) = arrow :-
   left == arrow.arg,

compiler/dialect_libraries/trino_library.py

@@ -16,6 +16,7 @@
 
 library = """
 ->(left:, right:) = {arg: left, value: right};
+`=`(left:, right:) = right :- left == right;
 
 ArgMin(a) = SqlExpr("(ARRAY_AGG({arg} order by {value}))[1]",
                     {arg: a.arg, value: a.value});

integration_tests/run_tests.py

@@ -69,6 +69,7 @@ def RunAll(test_presto=False, test_trino=False):
   RunTest("rec_small_cycle_test")
   RunTest("rec_cycle_test")
 
+  RunTest("sqlite_assignment_test")
   RunTest("sqlite_unwrapping_test")
   RunTest("sqlite_array_sub_test")
   RunTest("sqlite_combine_test")

integration_tests/sqlite_assignment_test.l

@@ -0,0 +1,44 @@
+#
+# Copyright 2023 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+@Engine("sqlite");
+
+StoreItem(name: "apple", price: 2.0);
+StoreItem(name: "banana", price: 1.0);
+StoreItem(name: "orange", price: 1.5);
+StoreItem(name: "pear", price: 3.0);
+
+PercentageDiscout(item_name: "apple", percentage: 10);
+PercentageDiscout(item_name: "orange", percentage: 20);
+
+CustomerPurchase(customer_name: "John", item_name: "apple", quantity: 2);
+CustomerPurchase(customer_name: "John", item_name: "banana", quantity: 1);
+CustomerPurchase(customer_name: "John", item_name: "orange", quantity: 3);
+CustomerPurchase(customer_name: "John", item_name: "orange", quantity: 3);
+CustomerPurchase(customer_name: "Jane", item_name: "pear", quantity: 1);
+CustomerPurchase(customer_name: "Jane", item_name: "banana", quantity: 2);
+CustomerPurchase(customer_name: "Jane", item_name: "apple", quantity: 2);
+
+@OrderBy(CustomerSavings, "customer_name");
+CustomerSavings(customer_name:,
+                total_savings? += savings,
+                max_fraction? Max= (fraction_savings = percentage / 100.0)) distinct :-
+  CustomerPurchase(customer_name:, item_name:, quantity:),
+  PercentageDiscout(item_name:),
+  StoreItem(name: item_name, price:),
+  PercentageDiscout(item_name:, percentage:),
+  savings = price * fraction_savings * quantity;
+
+Test := CustomerSavings();

integration_tests/sqlite_assignment_test.txt

@@ -0,0 +1,6 @@
++---------------+---------------+--------------+
+| customer_name | total_savings | max_fraction |
++---------------+---------------+--------------+
+| Jane          | 0.4           | 0.1          |
+| John          | 2.2           | 0.2          |
++---------------+---------------+--------------+

integration_tests/sqlite_file_test.l

@@ -18,9 +18,9 @@
 @Engine("sqlite");
 
 Test(result) :-
-  filename == "/tmp/sqlite_file_test_data.txt",
+  filename = "/tmp/sqlite_file_test_data.txt",
   WriteFile(filename, content: input_array) == "OK",
   input_array List= (x * 2 :- x in Range(10)),
-  read_data == ReadJson(filename),
+  read_data = ReadJson(filename),
   result_array List= (x :- x in read_data, x > 10),
-  result == Join(result_array, "/");
+  result = Join(result_array, "/");

parser_py/parse.py

@@ -571,7 +571,7 @@ def ParseLiteral(s):
 def ParseInfix(s, operators=None):
   """Parses an infix operator expression."""
   operators = operators or [
-      '||', '&&', '->', '==', '<=', '>=', '<', '>', '!=',
+      '||', '&&', '->', '==', '<=', '>=', '<', '>', '!=', '=',
       ' in ', '++?', '++', '+', '-', '*', '/', '%', '^', '!']
   unary_operators = ['-', '!']
   for op in operators:
@@ -671,6 +671,10 @@ def ParseConciseCombine(s: HeritageAwareString):
       prohibited_operators = ['!', '<', '>']
       if operator in prohibited_operators:
         return None
+      # Lowercase operators are not allowed and it would most likely mean
+      # that user forgot comma before assignment.
+      if operator[0].islower():
+        return None
       left_expr = ParseExpression(lhs)
       _, expression_body = SplitInOneOrTwo(combine, ':-')
       if expression_body:
@@ -786,6 +790,9 @@ def ParseGenericCall(s, opening, closing):
   if (s[idx] == opening and
       s[-1] == closing and
       IsWhole(s[idx + 1:-1])):
+    # Specialcasing `=` assignment operator for definition.
+    if predicate == '`=`':
+      predicate = '='
     return predicate, s[idx + 1: -1]