#+TITLE: Literate programming in F-Sharp using org-mode
#+DESCRIPTION: Use fsharp-babel in your Org spreadsheet
#+tags[]: emacs fsharp
#+DATE: 2017-06-17
#+SLUG: literate-programming-in-fsharp

[[http://orgmode.org/worg/org-contrib/babel/languages.html][Org Babel]] has a wide selection of supported programming languages.
But [[http://fsharp.org/][F#]] was still missing even though it's well suited for [[http://orgmode.org/worg/org-tutorials/org-spreadsheet-intro.html][Org
spreadsheets]] by the use of strongly typed access to connected
information via [[https://docs.microsoft.com/en-us/dotnet/fsharp/tutorials/type-providers/][type providers]]. So I started an implementation of [[https://github.com/juergenhoetzel/ob-fsharp][Org
Babel F#]] support.


In the following use case I adapted an [[https://www.gnu.org/software/emacs/manual/eintr.html][Emacs Lisp]] implementation for
[[https://vxlabs.com/2017/06/03/querying-restful-webservices-into-emacs-orgmode-tables/][querying the Kraken cryptocurrency exchange]]. I also used [[http://orgmode.org/cgit.cgi/org-mode.git/plain/lisp/ob-shell.el][Org Babel
Shell]] to install and use [[https://fsprojects.github.io/Paket/][Paket]]: a dependency manager for .NET.

The source file for this document can be found here: [[https://raw.githubusercontent.com/juergenhoetzel/blog.hoetzel.info/master/content/post/kraken-fsharp.org][kraken-fsharp.org]]

* Download Paket

Use [[https://curl.haxx.se/][curl]] to download the [[https://fsprojects.github.io/Paket/][Paket]] cli tool:

#+BEGIN_SRC bash
  curl -L  -z paket.exe -o paket.exe \
       https://github.com/fsprojects/Paket/releases/download/5.0.0/paket.exe
#+END_SRC

#+RESULTS:

* Install FSharp.Data

Reference [[http://fsharp.github.io/FSharp.Data/][FSharp.Data]] in the =paket.dependency= file:

#+BEGIN_SRC bash :tangle paket.dependencies :eval never
source https://nuget.org/api/v2
nuget FSharp.Data
#+END_SRC

Install the [[https://www.nuget.org/][NuGet]] dependencies into the packages folder using:

#+BEGIN_SRC bash :results silent
mono paket.exe install
#+END_SRC

* Access The Kraken Ticker Restservice

Instead of manually parsing the [[https://www.kraken.com/help/api][Kraken JSON API]] we let the compiler do
the job by using the [[http://fsharp.github.io/FSharp.Data/library/JsonProvider.html][JSON Type Provider]]. This Org Babel source block
named =ticker= will evaluate to a result block also named =ticker=
wich can be [[http://orgmode.org/manual/References.html][referenced]] from within an Org Table formula.

#+NAME: kraken
#+BEGIN_SRC fsharp :exports both
#r @"packages/FSharp.Data/lib/net45/FSharp.Data.dll"
open FSharp.Data

type Kraken = JsonProvider<"https://api.kraken.com/0/public/Ticker?pair=ETHEUR,XBTEUR">
let ticker = Kraken.GetSample()
[float <| ticker.Result.Xethzeur.C.[0]; float <| ticker.Result.Xxbtzeur.C.[0]]
#+END_SRC

#+RESULTS: kraken
| 338.97 | 5585.5 |

* Access the ticker result within an Org Table

The result can now be referenced in the following Org Table
using the formula ~@2$3 = remote(kraken, @1$1);%.2f~ for Ethereum
and ~@3$3 = remote(kraken, @1$2);%.2f~ for Bitcoin.


| Coin     | Units | Unit Price € | Current Value € | Fraction |
|----------+-------+--------------+-----------------+----------|
| Ethereum |     2 |       338.97 |          677.94 |     0.06 |
| Bitcoin  |     5 |      5585.50 |        27927.50 |     2.32 |
|----------+-------+--------------+-----------------+----------|
| Total    |     7 |              |        12021.85 |          |
|----------+-------+--------------+-----------------+----------|
#+TBLFM: @2$3=remote(kraken, @1$1);%.2f::@2$4..@3$4=@@#$2 * @@#$3;%.2f::@2$5=@2$4/@4$4;%.2f::@3$3=remote(kraken, @1$2);%.2f::@3$5=@3$4/@4$4;%.2f::@4$2=vsum(@II..III)::@4$4=vsum(@II..III)