&gt; I would like to see -- hint, I&#x27;m probably going to have to get my hands dirty! -- an implementation in either a dynamically typed language like Ruby&#x2F;Python&#x2F;Perl&#x2F;PHP&#x2F;Javascript&#x2F;… or a non-functional language like C&#x2F;C++&#x2F;Obj-C&#x2F;…<p>I understand where you&#x27;re coming from.  I&#x27;m working on a mini-ML in Python as a learning exercise for myself and possibly as a tutorial for others; will open source it soon.<p>As such, I&#x27;ve come across a few good resources:<p>check out Robert Small&#x27;s Hindley-Milner in Python[0], as well as alehander42&#x27;s Hermetic language in Python[1].<p>I also just found out about Hask, an implementation of many Haskell language features in Python.  Looking at the source code, it&#x27;s well-commented and clear, so I suspect I&#x27;ll learn a lot from it as well [2].<p>Finally, even though it&#x27;s not in a dynamic or non-functional language like you request, I highly recommend Andrej Bauer&#x27;s Programming Language Zoo[3], which contains very simple and easy-to-understand implementations of various type systems in OCaml. Very elucidating.<p>0. <a href="http:&#x2F;&#x2F;smallshire.org.uk&#x2F;sufficientlysmall&#x2F;2010&#x2F;04&#x2F;11&#x2F;a-hindley-milner-type-inference-implementation-in-python" rel="nofollow">http:&#x2F;&#x2F;smallshire.org.uk&#x2F;sufficientlysmall&#x2F;2010&#x2F;04&#x2F;11&#x2F;a-hind...</a><p>1. <a href="https:&#x2F;&#x2F;github.com&#x2F;alehander42&#x2F;hermetic" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;alehander42&#x2F;hermetic</a><p>2. <a href="https:&#x2F;&#x2F;github.com&#x2F;billpmurphy&#x2F;hask" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;billpmurphy&#x2F;hask</a><p>3. <a href="http:&#x2F;&#x2F;andrej.com&#x2F;plzoo&#x2F;" rel="nofollow">http:&#x2F;&#x2F;andrej.com&#x2F;plzoo&#x2F;</a><p>Edit: Oh, and one more resource that&#x27;s been <i>extremely</i> helpful has been &quot;Introduction to Functional Programming through Lambda Calculus&quot; by Michaelson.  Well worth the cost of the book.