much better comparison is to Haskell's extensible-effects, not IO.

Author: radix

README.rst

@@ -28,10 +28,10 @@ What Is It?
 ===========
 
 Effect lets you isolate your IO and state-manipulation code, by using a system
-somewhat similar to Haskell's ``IO`` monad (and `IOSpec`_). It also has
+very similar to Haskell's `extensible-effects`_ package. It also has
 similarities to Twisted's Deferred objects.
 
-.. _`IOSpec`: http://hackage.haskell.org/package/IOSpec
+.. _`extensible-effects`: https://hackage.haskell.org/package/extensible-effects
 
 The benefits of this are many: first, the majority of your code can become
 purely functional, leading to easier testing and ability to reason about