added about_equal function for sqlalchemy

odata_query/grammar.py

@@ -52,6 +52,7 @@
     "round": 1,
     "floor": 1,
     "ceiling": 1,
+    "aboutequal": 3,
     # Geo functions
     "geo.distance": 2,
     "geo.length": 1,

odata_query/sqlalchemy/common.py

@@ -2,6 +2,7 @@
 from typing import Any, Callable, Optional, Union
 
 from sqlalchemy.sql import functions
+from sqlalchemy import func
 from sqlalchemy.sql.expression import (
     BinaryExpression,
     BindParameter,
@@ -301,6 +302,13 @@ def func_ceiling(self, field: ast._Node) -> functions.Function:
     def func_floor(self, field: ast._Node) -> functions.Function:
         ":meta private:"
         return functions_ext.floor(self.visit(field))
+
+    def func_aboutequal(self, field: ast._Node, value: ast._Node, tolerance: ast._Node) -> functions.Function:
+        ":meta private:"
+        field = self.visit(field)
+        value = self.visit(value)
+        tolerance = self.visit(tolerance)
+        return operator.lt(func.abs(operator.sub(field, value)), tolerance)  
 
     def func_round(self, field: ast._Node) -> functions.Function:
         ":meta private:"

odata_query/typing.py

@@ -95,6 +95,7 @@ def infer_return_type(node: ast.Call) -> Optional[Type[ast._Node]]:
         "ceiling",
         "floor",
         "round",
+        "aboutequal",
         "geo.distance",
         "geo.length",
     ):