rdblue commented on code in PR #4816:
URL: https://github.com/apache/iceberg/pull/4816#discussion_r917458529
##########
python/pyiceberg/expressions/base.py:
##########
@@ -131,11 +75,115 @@ def __ge__(self, other):
class BooleanExpression(ABC):
- """base class for all boolean expressions"""
+ """Represents a boolean expression tree."""
@abstractmethod
def __invert__(self) -> "BooleanExpression":
- ...
+ """Transform the Expression into its negated version."""
+
+
+class Bound(Generic[T], ABC):
+ """Represents a bound value expression."""
+
+ def eval(self, struct: StructProtocol): # pylint: disable=W0613
+ ... # pragma: no cover
+
+
+class Unbound(Generic[T, B], ABC):
+ """Represents an unbound expression node."""
+
+ @abstractmethod
+ def bind(self, schema: Schema, case_sensitive: bool) -> B:
+ ... # pragma: no cover
+
+
+class Term(ABC):
+ """An expression that evaluates to a value."""
+
+
+class BaseReference(Generic[T], Term, ABC):
+ """Represents a variable reference in an expression."""
+
+
+class BoundTerm(Bound[T], Term):
+ """Represents a bound term."""
+
+
+class UnboundTerm(Unbound[T, BoundTerm[T]], Term):
+ """Represents an unbound term."""
+
+
+@dataclass(frozen=True)
+class BoundReference(BoundTerm[T], BaseReference[T]):
+ """A reference bound to a field in a schema
+
+ Args:
+ field (NestedField): A referenced field in an Iceberg schema
+ accessor (Accessor): An Accessor object to access the value at the
field's position
+ """
+
+ field: NestedField
+ accessor: Accessor
+
+ def eval(self, struct: StructProtocol) -> Any:
Review Comment:
I think that this should return `T`. That's the type that this reference
produces. That may be a little difficult since `Accessor` is not parameterized
by the type that it returns. If it is hard, we can fix it later.
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