Add ok_or and ok_or_else methods. (#15)

Fixes #9

.github/workflows/ci.yml

@@ -38,7 +38,7 @@ jobs:
 
       # Install library
       - name: Install maybe
-        run: pip install --root-user-action=ignore --editable .
+        run: pip install --root-user-action=ignore --editable .[result]
 
       # Tests
       - name: Run tests (excluding pattern matching)

Makefile

@@ -7,7 +7,7 @@ PYTHON_PRE_310 := $(shell python -c "import sys; print(sys.version_info < (3, 10
 install: phony
 	@echo Installing dependencies...
 	python -m pip install --require-virtualenv -r requirements-dev.txt
-	python -m pip install --require-virtualenv -e .
+	python -m pip install --require-virtualenv -e .[result]
 
 lint: phony lint-flake lint-mypy
 
@@ -23,7 +23,7 @@ lint-mypy: phony
 	mypy
 
 test: phony
-	pytest
+	pytest -vv
 
 docs: phony
 	lazydocs \

README.md

@@ -1,6 +1,10 @@
 # Maybe
 
+[![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)
+[![PyPI - Python Version](https://img.shields.io/pypi/pyversions/rustedpy-maybe?logo=python&logoColor=white)](https://pypi.org/project/rustedpy-maybe/)
+[![PyPI](https://img.shields.io/pypi/v/rustedpy-maybe)](https://pypi.org/project/rustedpy-maybe/)
 [![GitHub Workflow Status (branch)](https://img.shields.io/github/actions/workflow/status/rustedpy/maybe/ci.yml?branch=master)](https://github.com/rustedpy/maybe/actions/workflows/ci.yml?query=branch%3Amaster)
+[![Checked with mypy](https://www.mypy-lang.org/static/mypy_badge.svg)](http://mypy-lang.org/)
 [![Coverage](https://codecov.io/gh/rustedpy/maybe/branch/master/graph/badge.svg)](https://codecov.io/gh/rustedpy/maybe)
 
 A simple Maybe (Option) type for Python 3 [inspired by Rust](
@@ -20,6 +24,23 @@ Latest GitHub `master` branch version:
 pip install git+https://github.com/rustedpy/maybe
 ```
 
+There are no dependencies outside of the Python standard library.  However, if
+you wish to use the `Result` conversion methods (see examples in the next
+section), you will need to install the `result` extra.
+
+In this case, rather than installing via one of the commands above, you can
+install the package with the `result` extra either from the latest release:
+
+```sh
+pip install rustedpy-maybe[result]
+```
+
+or from the GitHub `master` branch:
+
+```sh
+pip install git+https://github.com/rustedpy/maybe[result]
+```
+
 ## Summary
 
 **Experimental. API subject to change.**
@@ -28,7 +49,7 @@ The idea is that a possible value can be either `Some(value)` or `Nothing()`,
 with a way to differentiate between the two. `Some` and `Nothing` are both
 classes encapsulating a possible value.
 
-Example usage,
+Example usage:
 
 ```python
 from maybe import Nothing, Some
@@ -39,6 +60,25 @@ assert o.unwrap_or_else(str.upper) == 'yay'
 assert n.unwrap_or_else(lambda: 'default') == 'default'
 ```
 
+There are some methods that support conversion from a `Maybe` to a `Result` type
+in the [result library](https://github.com/rustedpy/result/).  If you wish to
+leverage these methods, you must install the `result` extra as described in the
+installation section.
+
+Example usage:
+
+```python
+from maybe import Nothing, Some
+from result import Ok, Err
+
+o = Some('yay')
+n = Nothing()
+assert o.ok_or('error') == Ok('yay')
+assert o.ok_or_else(lambda: 'error') == Ok('yay')
+assert n.ok_or('error') == Err('error')
+assert n.ok_or_else(lambda: 'error') == Err('error')
+```
+
 ## Contributing
 
 These steps should work on any Unix-based system (Linux, macOS, etc) with Python