JavaScript to Haskell

By Jesse Tomchak

Recovering iOS developers, exploring functional languages while daily working with JavaScript and React... more

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How many episodes does JavaScript to Haskell have?

The podcast currently has 9 episodes available.

JavaScript to Haskell episodes:

September 06, 201808: Docker
Deploy early and often
I want to send this into ‘PROD’ bc running locally is only ½ the battle or less
After spinning my wheels reading a dozen things. Including using a makefile? oh boy. I needed to reset.
Pretty sure I got wrapped up in the ‘what i don’t know’ and lost sight of the “oh yeah”, i’ve done something like that a bit, right?
Resources
zeit
Creating your own Scotty
Haskell Dockerfile
failed makefile
fpcomplete building haskell with docker
Scotty Example with DB
docker slimming
multistage
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JavaScript to Haskell
Twitter: @jstoHaskell()
Site: JSToHaskell
microblog: @jtomchak
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Twitter: @jtomchak
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August 25, 201807: JSON Payloads
Returning actual Data in Json
Building out some hardcoded users
need to supply User before the data
don’t forget the = sign
We could manually build the encode and decode to/from JSON, but Generics, lets you automatically do things based on the data type
adding {-# LANGUAGE DeriveGeneric #-} and import GHC.Generics
don’t forget to add instance
instance ToJSON User
instance FromJSON User
Now we are able to see the output of having the generic encoder
Ok, two modules loaded.
*Main Lib> import Data.Aeson (encode)
*Main Lib Data.Aeson> encode bob
"{\"userName\":\"Bobby Boy\",\"userId\":1}"
And now with that it looks like Scotty has a function json for use to return a json payload. sweet
get "/users" $ do
json allUsers
Resources
Following this guide a bit
Aeson
Scotty
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JavaScript to Haskell
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August 23, 201806: Routed Params
tackling route params
This is really nice that it’s a lot like express
We can add route parameters with :xxx in the url, just like Sinatra and express. To read it in our handler, we use the param function. Edit the /hello route to be this
get "/hello/:name" $ do
name <- param "name"
text ("hello " <> name <> "!")
Tried this, got some errors. realized that Haskell has a ton of ideas about strings. Like Text.
Text errors
‘Text’ is defined in ‘Data.Text.Internal’
‘Data.Text.Internal.Lazy.Text’
is defined in ‘Data.Text.Internal.Lazy’
Resources
Guide
Text Types
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JavaScript to Haskell
Twitter: @jstoHaskell()
Site: JSToHaskell
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August 16, 201805: Routes In Haskell
Building on our Server API, we want to break down the function called by the route into something more compose-able
Route Type
get :: RoutePattern -> ActionM () -> ScottyM ()
That’s a get request
Resources
docker quick
Sean Hess original post
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JavaScript to Haskell
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August 15, 201804: Practical Haskell
So, following the book is hard. I don’t really learn well that way. I have just enough knowledge that the first part feels boring and repetitive, but I don’t know what I don’t know, so where do I pick up, chapter 2 or maybe 3? So let’s take this from a real JS perspective.
Building an API
So we know how to get and return json with HTTP requests in Node, how do we do it in Haskell? Ok, now build on that.
Make it something relatable.
stack new hs-webapi
Go into /package.yaml and under dependencies add ‘scotty’ and ‘aeson’
Then run stack build
… then wait (forgotten the compile times :eye_roll:) also 67 dependencies. I mean it’s not 867!!!!
..still waiting.
Resources
Building an API
scotty
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JavaScript to Haskell
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August 09, 201803: Lists
03: Lists
Handling Lists
Before we get started a couple tips for shorthand in Prelude
* > GHCi is an interactive Haskell REPL (Read-Eval-Print-Loop) that comes with GHC. At the GHCi prompt, you can evaluate expressions, load Haskell files with :load (:l) (and reload them with :reload (:r)), ask for the type of an expression with :type (:t), and many other things (try :? for a list of commands).
* using let in the GHCI
Words are are a list of chars
In Haskell, lists are a homogenous data structure. It stores several elements of the same type.
One of the most basic data types in Haskell
List comprehensions?
Like set comprehensions, normally used for building more specific sets from a larger general set
*
List Constructing
we should mention type signatures too
NOT AN ARRAY
ugh, what’s this mean
intListLength (x:xs) = 1 + intListLength xs
Resources
CIS 194
Real World Haskell
Learn You a Haskell
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JavaScript to Haskell
Twitter: @jstoHaskell()
Site: JSToHaskell
microblog: @jtomchak
Jesse Tomchak
Twitter: @jtomchak
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August 08, 201802: Tooling
02: Haskell Tools
Install
stack looks to be the sort of NPM of haskell
reproduceable builds,
YAML file config. cabal config too
Command Line
stack build and then stack exec hello-world-exe
the build will create an executable in the ./stack-work and look there for executables. cool
The Setup.hs file is a component of the Cabal build system which stack uses. It’s technically not needed by stack, but it is still considered good practice in the Haskell world to include it. The file we’re using is straight boilerplate:
Ok so cabal is a build system that stack uses, but good practice.
It is also important to remember that stack is built on top of the Cabal build system. Therefore, an understanding of the moving parts in Cabal are necessary. In Cabal, we have individual packages, each of which contains a single .cabal file. The .cabal file can define 1 or more components: a library, executables, test suites, and benchmarks. It also specifies additional information such as library dependencies, default language pragmas, and so on.
So it looks like cabal is the actual package builder and stack is a sort of management tool for haskell language, cabal, and all the other bits/pieces
Which ghc is it using?
jtomchak@MeowBook:/c/Users/jtomc/Documents/Haskell/hello-world$ stack exec -- which ghc
/home/jtomchak/.stack/programs/x86_64-linux/ghc-8.4.3/bin/ghc
Macros ?
{-# LANGUAGE OverloadedStrings #-}
not sure what the line means ?
appears to be some sort of compile macro ?
Resources
* [Install](https://docs.haskellstack.org/en/stable/install_and_upgrade/)
Follow
JavaScript to Haskell
Twitter: @jstoHaskell()
Site: JSToHaskell
microblog: @jtomchak
Jesse Tomchak
Twitter: @jtomchak
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August 06, 201801: Haskell Quick Rundown
Episode 1:
* Learning path github.com/bitemyapp…
* Functional
* Two values of functional
* Functions are first-class, that is, functions are values which can be used in exactly the same ways as any other sort of value.
* The meaning of Haskell programs is centered around evaluating expressions rather than executing instructions.
* Pure
Haskell expressions are always referentially transparent, that is:
* No mutation! Everything (variables, data structures…) is immutable.
* Expressions never have “side effects” (like updating global variables or printing to the screen).
* Calling the same function with the same arguments results in the same output every time.
* Lazy
* Statically Typed
* Helps clarify thinking and express program structure
* Serves as a form of documentation
* Turns run-time errors into compile-time errors
*
Themes
Types
Abstraction
Whole meal programming
Follow
JavaScript to Haskell
Twitter: @jstoHaskell()
Site: JSToHaskell
microblog: @jtomchak
Jesse Tomchak
Twitter: @jtomchak
...more
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August 01, 2018 00: Pilot
We cover the why of trying to move into Haskell, the format of the show, and what to expect moving forward.
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0min

FAQs about JavaScript to Haskell:

How many episodes does JavaScript to Haskell have?

The podcast currently has 9 episodes available.