# New Meetup new place.
18:30 - Coming together
19:00 - Theorems for Free by Fabricio
19:45 - All you wanted to know about Recursion by Paul Heymann
## Theorems for Free
speaker: Fabricio de Sousa Nascimento
categories: type system
If the type of a polymorphic function is a theorem, every valid function implementation is a proof. In this talk, I plan to show how we can use this result in a very pragmatic way in order to guess (or even know for certain) what a function does only by looking at its type.
In this talk I intend to answer the following questions:
How to read Haskell type notation (Hindley-Milner ) and how to use it to represent types in any language? How can we tell how many inhabitants a type has? How can that help us to guess what a function does? How can I apply that knowledge to common functions (id, head, fold, map)? 
 - https://en.wikipedia.org/wiki/Hindley%E2%80%93Milner_type_system
 - https://www.cs.sfu.ca/CourseCentral/831/burton/Notes/July14/free.pdf
Fabs recently started a journey into the depths of Haskell after a few years experimenting with Scala. He is currently a Software Engineer at Mesosphere where he works with the UI team helping the adoption of the Functional Paradigm to tame the complexity of the distributed operating system DC/OS.
## All you wanted to know about Recursion
speaker: Paul Heymann (yeah me again :) )
categories: pl, Haskell, Scala
What the title says. This will be a talk about recursive data structures and functions. We will see what kinds of recursion exist, how they work with different evaluation strategies, or what we have to do to make them work, and why we use it at all.