✨ feat(frames): new function frame_of

src/coordinax/_src/frames/__init__.py

@@ -11,12 +11,13 @@
     "NoFrame",
     "TransformedReferenceFrame",
     "frame_transform_op",
+    "frame_of",
     # Coordinate
     "AbstractCoordinate",
     "Coordinate",
 ]
 
-from .api import frame_transform_op
+from .api import frame_of, frame_transform_op
 from .base import AbstractReferenceFrame
 from .coordinate import AbstractCoordinate, Coordinate
 from .errors import FrameTransformError

src/coordinax/_src/frames/api.py

@@ -15,3 +15,8 @@ def frame_transform_op(
     /,
 ) -> Any:
     """Make a frame transform."""
+
+
+@dispatch.abstract
+def frame_of(obj: Any, /) -> Any:
+    """Get the frame of an object."""

src/coordinax/_src/frames/base.py

@@ -111,3 +111,22 @@ def from_(
         raise TypeError(msg)
 
     return obj
+
+
+# ---------------------------
+# Frame API
+
+
+@dispatch
+def frame_of(obj: AbstractReferenceFrame, /) -> AbstractReferenceFrame:
+    """Get the frame of an `coordinax.frames.AbstractReferenceFrame`.
+
+    Examples
+    --------
+    >>> import coordinax.frames as cxf
+    >>> frame = cxf.ICRS()
+    >>> frame_of(frame) is frame
+    True
+
+    """
+    return obj

src/coordinax/_src/frames/coordinate.py

@@ -123,6 +123,23 @@ def __str__(self) -> str:
         return f"{type(self).__name__}(\n{str_fs}\n)"
 
 
+@dispatch
+def frame_of(obj: AbstractCoordinate) -> AbstractReferenceFrame:
+    """Return the frame of the coordinate.
+
+    Examples
+    --------
+    >>> import coordinax as cx
+
+    >>> coord = cx.Coordinate(cx.CartesianPos3D.from_([1, 2, 3], "kpc"),
+    ...                       cx.frames.ICRS())
+    >>> cx.frame_of(coord)
+    ICRS()
+
+    """
+    return obj.frame
+
+
 ##############################################################################
 
 

src/coordinax/frames.py

@@ -48,6 +48,7 @@
     "NoFrame",
     "TransformedReferenceFrame",
     "frame_transform_op",
+    "frame_of",
     # Coordinates
     "AbstractCoordinate",
     "Coordinate",
@@ -65,6 +66,7 @@
         FrameTransformError,
         NoFrame,
         TransformedReferenceFrame,
+        frame_of,
         frame_transform_op,
     )