add lang.gpu to api docs

docs/source/api/lang.rst

@@ -41,3 +41,9 @@ Implementation
 
 .. automodule:: pystencilssfg.lang.cpp
     :members:
+
+GPU Runtime APIs
+----------------
+
+.. automodule:: pystencilssfg.lang.gpu
+    :members:

src/pystencilssfg/lang/gpu.py

@@ -5,38 +5,50 @@ from typing import Protocol
 from .expressions import CppClass, cpptype, AugExpr
 
 
-class _Dim3Base(CppClass):
+class Dim3Interface(CppClass):
+    """Interface definition for the ``dim3`` struct of Cuda and HIP."""
+
     def ctor(self, dim0=1, dim1=1, dim2=1):
+        """Constructor invocation of ``dim3``"""
         return self.ctor_bind(dim0, dim1, dim2)
 
     @property
-    def x(self):
+    def x(self) -> AugExpr:
+        """The `x` coordinate member."""
         return AugExpr.format("{}.x", self)
 
     @property
-    def y(self):
+    def y(self) -> AugExpr:
+        """The `y` coordinate member."""
         return AugExpr.format("{}.y", self)
 
     @property
-    def z(self):
+    def z(self) -> AugExpr:
+        """The `z` coordinate member."""
         return AugExpr.format("{}.z", self)
 
     @property
-    def dims(self):
-        """The dims property."""
-        return [self.x, self.y, self.z]
+    def dims(self) -> tuple[AugExpr, AugExpr, AugExpr]:
+        """`x`, `y`, and `z` as a tuple."""
+        return (self.x, self.y, self.z)
 
 
 class ProvidesGpuRuntimeAPI(Protocol):
+    """Protocol definition for a GPU runtime API provider."""
 
-    dim3: type[_Dim3Base]
+    dim3: type[Dim3Interface]
+    """The ``dim3`` struct type for this GPU runtime"""
 
     stream_t: type[AugExpr]
+    """The ``stream_t`` type for this GPU runtime"""
 
 
 class CudaAPI(ProvidesGpuRuntimeAPI):
+    """Reflection of the CUDA runtime API"""
+
+    class dim3(Dim3Interface):
+        """Implements `Dim3Interface` for CUDA"""
 
-    class dim3(_Dim3Base):
         template = cpptype("dim3", "<cuda_runtime.h>")
 
     class stream_t(CppClass):
@@ -44,8 +56,11 @@ class CudaAPI(ProvidesGpuRuntimeAPI):
 
 
 class HipAPI(ProvidesGpuRuntimeAPI):
+    """Reflection of the HIP runtime API"""
+
+    class dim3(Dim3Interface):
+        """Implements `Dim3Interface` for HIP"""
 
-    class dim3(_Dim3Base):
         template = cpptype("dim3", "<hip/hip_runtime.h>")
 
     class stream_t(CppClass):