notes on returns

20240403221816-returns.org

@@ -0,0 +1,49 @@
+:PROPERTIES:
+:ID:       4276e1de-1ac5-4e4d-896c-1601e2e61a4e
+:END:
+#+title: Returns
+
+A library implementing various [[id:8ee5037f-0673-4968-9ec4-184bf31dd72d][Monads]] in [[id:cda9c620-fec5-4549-b979-22fc06819d77][Python]].
+
+* Benefits
+** Explicit errors
+** Composition
+*** Asynchronous composition
+* Drawbacks
+** Learning curve
+** Formatting call chains in YAPF
+Call chaining formats poorly in YAPF. Consider the following example which
+performs the following steps:
+1. Builds a request object
+2. Wraps the request object in a Future
+3. Binds the request to the HTTP send method
+4. Binds the result to a response handler
+
+The code, formatted by YAPF, looks like this:
+
+#+begin_src python
+  return FutureResult.from_result(
+      self.build_request(request)).bind_async(safe_send).bind_result(
+          self.load_response)
+#+end_src
+
+The same code, formatted instead by the Black formatter, looks like this:
+
+#+begin_src python
+          return (
+              FutureResult.from_result(self.build_request(request))
+              .bind_async(safe_send)
+              .bind_result(self.load_response)
+          )
+#+end_src
+
+A workaround is to use the =pointfree= module from =returns=, though this comes
+with the additional overhead of understanding and using the point-free
+functions.
+#+begin_src python
+  return flow(
+      FutureResult.from_result(self.build_request(request)),
+      pointfree.bind_async(safe_send),
+      pointfree.bind_result(self.load_response),
+  )
+#+end_src