initial Dimension protocol

.gitattributes

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+# SCM syntax highlighting
+pixi.lock linguist-language=YAML linguist-generated=true

.gitignore

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+
+# pixi environments
+.pixi
+*.egg-info

pyproject.toml

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+[project]
+authors = [{ name = "quantity-dev contributors" }]
+dependencies = []
+name = "dimension-api"
+requires-python = ">= 3.12"
+version = "0.0.1.dev0"
+
+[build-system]
+build-backend = "hatchling.build"
+requires = ["hatchling"]
+
+[tool.pixi.project]
+channels = ["https://prefix.dev/conda-forge"]
+platforms = ["win-64", "linux-64", "osx-64", "osx-arm64"]
+
+[tool.pixi.pypi-dependencies]
+dimension_api = { path = ".", editable = true }

src/dimension_api/__init__.py

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+"""Dimension API."""
+
+from typing import Final, Protocol, Self, runtime_checkable
+
+__version__: Final = "0.0.1.dev0"
+__all__ = ["__version__", "Dimension"]
+
+@runtime_checkable
+class Dimension(Protocol):
+    @property
+    def is_dimensionless(self) -> bool: ...
+
+    def __mul__(self, other: Self, /) -> Self: ...
+    def __truediv__(self, other: Self, /) -> Self: ...
+    def __pow__(self, other: int, /) -> Self: ...