Open xmnlab opened 1 month ago
example from python ast:
>>> ast.dump(ast.parse("a[1]"))
"Module(body=[Expr(value=Subscript(value=Name(id='a', ctx=Load()), slice=Constant(value=1), ctx=Load()))], type_ignores=[])"
>>> ast.dump(ast.parse("a[0:1]"))
"Module(body=[Expr(value=Subscript(value=Name(id='a', ctx=Load()), slice=Slice(lower=Constant(value=0), upper=Constant(value=1)), ctx=Load()))], type_ignores=[])"
>>> ast.dump(ast.parse("a[:,:]"))
"Module(body=[Expr(value=Subscript(value=Name(id='a', ctx=Load()), slice=Tuple(elts=[Slice(), Slice()], ctx=Load()), ctx=Load()))], type_ignores=[])"
>>> ast.dump(ast.parse("a[:,:,:]"))
"Module(body=[Expr(value=Subscript(value=Name(id='a', ctx=Load()), slice=Tuple(elts=[Slice(), Slice(), Slice()], ctx=Load()), ctx=Load()))], type_ignores=[])"
from gpt:
Updating the Design to Support Slices
In Python's AST, the
Subscript
node has aslice
attribute that can be:Constant
(for single indices, e.g.,a[1]
).Slice
(for slices, e.g.,a[0:1]
).Tuple
of slices or indices (e.g.,a[:,:]
,a[:,:,:]
).We'll mimic this behavior in our
astx
module by:SliceExpr
class to represent slices (e.g.,start:stop:step
).IndexExpr
to accept either a singleExpr
(for simple indices) or a list ofExpr
(for multi-dimensional indexing).1. Defining
SliceExpr
First, let's create the
SliceExpr
class.Explanation:
Expr
.lower
: The lower bound (inclusive) of the slice, can beNone
.upper
: The upper bound (exclusive) of the slice, can beNone
.step
: The step size of the slice, can beNone
.__str__
: Provides a readable string representation.get_struct
: For structured representation.Note: We need to add
SliceExprKind
toASTKind
.2. Updating
ASTKind
EnumAdd the new kind for
SliceExpr
.3. Modifying
IndexExpr
Modify
IndexExpr
to accept either a single index (Expr
) or a list of indices (list ofExpr
), which can includeSliceExpr
instances.Explanation:
Expr
(e.g., fora[1]
).Expr
instances (e.g., fora[:, :]
,a[0:1, :]
), which can beSliceExpr
or otherExpr
types.__str__
Method: Adjusted to handle both single index and list of indices.get_struct
Method: Adjusted accordingly.Example Usage
Let's revisit your examples and see how we can represent them using the updated
IndexExpr
and the newSliceExpr
.1.
a[1]
Output:
2.
a[0:1]
Output:
3.
a[:,:]
Output:
4.
a[:,:,:]
Output:
Handling Slices with Step
For completeness, let's handle slices with steps, e.g.,
a[::2]
.Output:
Integration with Existing Structures
None
to represent missing values in slices, we might need aLiteralNone
class inastx.datatypes
.Alternatively, since slices often have
None
for missing values, and ourSliceExpr
allowslower
,upper
, andstep
to beNone
, we can avoid needing aLiteralNone
and represent missing values byNone
.Testing and Validation
IndexExpr
andSliceExpr
integrate correctly with other expressions and statements in your AST.astx.viz
to visualize complex indexing and slicing structures.Conclusion
By introducing the
SliceExpr
class and updating theIndexExpr
class, we've extended theastx
module to fully support slicing, similar to Python's ASTSubscript
node. This enhancement allows you to represent a wide range of indexing operations, including single indices, slices, and multi-dimensional indexing with slices.Final Notes
Updates to
astx/__init__.py
: AddSliceExpr
to the exports.Ensure All Necessary Imports: Make sure all necessary classes and modules are imported where needed.
Documentation: Update docstrings and module documentation to reflect the new capabilities.
Testing: Write comprehensive tests covering various slicing scenarios to validate the correctness of your implementation.