debasishg

Join based queries with skunk decoders - folding with a Semigroup

Domain Model

Let's take a simple example that models an employee along with the salaries accrued in a year. Here's the domain model in Scala:

case class Salary(empId: String, month: Int, amount: BigDecimal)
case class Employee(id: String, name: String, salaries: List[Salary])

debasishg

1. Graph Convolution Network - a blog post and the associated tweet. Check for the video.
2. Deep Graph Library
3. Machine Learning on Graphs: A Model and Comprehensive Taxonomy by Ines Chami, Sami Abu-El-Haija, Bryan Perozzi, Christopher Ré, Kevin Murphy
4. Relational inductive biases, deep learning, and graph networks by Peter W. Battaglia, Jessica B. Hamrick, Victor Bapst, Alvaro Sanchez-Gonzalez, Vinicius Zambaldi, Mateusz Malinowski, Andrea Tacchetti, David Raposo, Adam Santoro, Ryan Faulkner, Caglar Gulcehre, Francis Song, Andrew Ballard, Justin Gilmer, George Dahl, Ashish Vaswani, Kelsey Allen, Charles Nash, Victoria Langston, Chris Dyer, Nicolas Heess, Daan Wierstra, Pushmeet Kohli, Matt Botvinick, Oriol Vinyals, Yujia Li, Razvan Pascanu - For the intuition of what GNNs can achieve, what the pro

debasishg

Original : hasura/graphql-engine#2933 (comment)

Yes, that’s right. It never makes sense to use foldl on lists because it never has any benefit and will always leak space.

To explain why, I wrote a mini blog post explaining the difference between foldl and foldr in Haskell. To start, you have to understand that foldl and foldr are not folds “from the left” and “from the right.” Both foldl and foldr traverse the structure in the same order, which in the case of lists means left to right. The difference is the fold’s associativity.

debasishg

https://ocharles.org.uk/posts/2016-01-26-transformers-free-monads-mtl-laws.html
https://www.reddit.com/r/haskell/comments/f995kd/pawe%C5%82_szulc_maintainable_software_architecture_in/
https://www.reddit.com/r/haskell/comments/7ar5jy/free_monad_or_monad_transformer_to_manage_effects/
https://mail.haskell.org/pipermail/haskell-cafe/2018-September/129992.html
https://mail.haskell.org/pipermail/haskell-cafe/2018-September/129988.html (thread)
https://www.reddit.com/r/haskell/comments/3nkv2a/why_dont_we_use_effect_handlers_as_opposed_to/
https://lexi-lambda.github.io/blog/2017/04/28/lifts-for-free-making-mtl-typeclasses-derivable/
https://www.reddit.com/r/haskell/comments/66pzc8/recommended_way_to_use_monad_transformers/
https://making.pusher.com/3-approaches-to-monadic-api-design-in-haskell/
https://www.reddit.com/r/haskell/comments/ej8fme/unordered_effects/fd00mk2/?context=1

debasishg

Keeping a remote fork in sync
-----------------------------
git status
git checkout master
git remote -v
git remote add upstream https://github.com/lightbend/cloudflow.git
git remote -v
git fetch upstream
git pull upstream master
git push origin master

debasishg

Visitor Pattern

• A Type-theoretic Reconstruction of the Visitor Pattern by Peter Buchlovsky and Hayo Thielecke
• The VISITOR Pattern as a Reusable, Generic, Type-Safe Component by Bruno C. d. S. Oliveira, Meng Wang, and Jeremy Gibbons
• Scala and the visitor pattern by Travis Brown and a reddit discussion
• Visitor Pattern, Catamorphism and Algebraic Data Type by Alexandre Bertails
• Modular domain-specific language components in scala by Christian Hofer and Klaus Ostermann
• Towards improved GADT reasoning in Scala by EPFL
• [EVF: An Extensible a

debasishg

Can we do it with `ClassTag` ?

Adriaan: 
You can't with a class tag, as it represents the erased type as known to the JVM. You could use a TypeTag 
to reify the full type, but that depends on full scala reflection, which has its own downsides 
(not thread safe, basically pulls in the compiler,...)

scala> import scala.reflect.runtime.universe.TypeTag
import scala.reflect.runtime.universe.TypeTag

debasishg

trait Coercible[A, B] {
  def coerce(a: A): B
}

def coerce[A, B](a: A)(implicit coerceAB: Coercible[A, B]): B = {
  coerceAB.coerce(a)
}

trait Newtype[+T] {
  val value: T

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Installing Postgres via Brew

Pre-Reqs

Brew Package Manager

In your command-line run the following commands:

1. brew doctor
2. brew update

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# start postgresql
pg_ctl -D /usr/local/var/postgres start

# stop postgresql
pg_ctl -D /usr/local/var/postgres stop