Tag Archives: fsharp

Setting up quick API with F# and Azure Functions

As mentioned in my last week Elixir blog post, I produced some quick fake API based on Azure Functions. I thought it’s gonna take a couple of minutes, but it turned out to be a whole adventure in itself.

The creating of a function is a breeze.

  1. Go to Portal, click big green “+” sign and search for “Function App”Screen Shot 2017-04-17 at 16.34.00.png
  2. Pick Function App published by Microsoft
  3. Fill all the necessary fields like App name (must be globally unique) or location. For hosting plan I used “Consumption plan” which means, I pay only for the time that function is running. I also like to pin my stuff to the dashboard, so it’s easier to find.Screen Shot 2017-04-17 at 16.37.38.png
  4. It will take several minutes to deploy.
  5. Now you can create your functions for the app. F# is hidden in small print just above “Create this function” button. So click “create your own custom function”.Screen Shot 2017-04-17 at 16.40.40.png
  6. Then with Language drop-down, pick “F#” and for Scenario – “API  & Webhooks”. There should be on the F# function triggered by HTTP request. That’s the one you want for API.
  7. You’ll get premade piece of code with a simple function that is triggered by HTTP POST with name object and responses “Hello “.

Then I started writing the logic I wanted. I made an array of hard coded airport data. I made the function to accept only GET requests (you can change it in function.json file). In code, I parse query strings and get the airport IATA code. If I have this airport in my array, I response 200 with JSON containing the data. Otherwise, I return 404. If there’s no parameter in the query string, function answers with 500.

It’s relatively simple and straightforward F# code. I just struggled a lot with debugging. The small editor on Azure doesn’t give you static analysis, nor type information and no squigglies. You need to run the function and check for compilation errors or runtime errors. There was also some weird scoping behaviour, that forced me to declare the Airports array within the function. Anyways, after 2hrs I had an API that did what I wanted. You can see the code below. It’s not bulletproof, but it does the job. And I got to play with Azure Functions a bit.

https://gist.github.com/mlusiak/5053aabbc1c6e76db082dc8daa952c81

If you want to read more about other types of F# Azure Functions, Mathias Brandewinder wrote recently two posts about timer and queue triggered functions.

That’s all for today. Tune in next week for another part. Also, check previous episodesAnd if you’re interested in machine learning, look into my weekly link drop.

Elixir vs F# – opinionated syntax comparison

Note: There are some awesome comments to this post that add a lot of value. Please check them below.

This is the second part of my Elixir adventures and another post for “Get Noticed” competition.

I was planning to start furiously coding on my project for this second post and start building some web API with Phoenix. But Gutek suggested, that first I should really dig into some internals that will help me understand how Phoenix works – thanks for this advice. On top of that, I didn’t really have time to dig properly, but I managed to look a bit into syntax and I have mixed feelings.

I won’t be doing an introduction to Elixir post here. You can find a lot of resources on that, for example, Gutek’s series in Polish, official documentation or this short article. Instead, I’m gonna compare it to something that I’m familiar with –  F# syntax. And it’s nowhere near comprehensive comparison. Just a few things that I found interesting and worth noting.

Comparing stuff

Right from the start, there are few differences here. F# uses just ‘=’
to compare if two things are equal. Elixir has two comparison operators ‘==’ and ‘===’. First one is standard compare operator. Second, from my current understanding, is useful mostly for comparing if numbers are of the same type. To explain, look at this example:

// F#
1 = 2             // false
1 = 1             // true

1 = 1.0           // This yields compile error
float(1) = 1.0    // true

Although we didn’t declare any types in F#, it will infer them during compilation. And as a strongly typed language, will not allow comparing values of two different types.

# Elixir
1 == 2            # false
1 == 1            # true

1 == 1.0          # true
1 === 1.0         # false

Elixir is dynamically typed. It means, that it will also infer types, but this will happen in the runtime and also will do casts for you.

For not-equal F# uses ‘<>’ and Elixir ‘!=’ and ‘!==’. Generally, Elixir is here more consistent with most programming languages, so I’ll give it a point here, but I appreciate type safety of F# also. You can also notice that those languages use a different convention for comments.

In Elixir ‘=’ is also used for matching which is quite powerful.

Immutability

Although both languages are immutable by default, there are some differences in approach.

In Elixir, value is immutable so you cannot change it, but you can assign the “label” to some other value.

# Elixir
a = 1             # value "1" is now labelled "a"
a = a+1           # label "a" is changed: now "2" is labelled "a"
a = a*5           # value "10" is now labelled "a"

But if you want to refer to the current value of, i.e. when using match operator, you can do it this way:

# Elixir
b = 1
b = 2             # rebinding variable to 2
^b = 3            # matching: 2 = 3 -> error

First thing that came to my mind when saw it, were C language pointers :)

F# allows mutability, but it has to be openly declared, and then you need a different operator to change the value. Mutability is mostly allowed for compatibility reasons with .NET libraries, so you shouldn’t abuse it.

// F#
let a = 1         // binding value "1"" to label "a"
a = 2             // returns false (it is just comparing)
a <- 2            // compile error

let mutable b = 1 // binding value "1"" to mutable variable "b""
b <- 2            // changing value of variable "b""
b = 2             // returns true

In this part, F# is for me clear winner. You cannot change value bind to a label. It is much less confusing and makes more readable code.

List operations

List operations are generally very similar. What I found interesting in Elixir, you can match not only head and tail, like in F# but several first elements:
EDIT: As anonguy pointed out in the comments, that’s also possible in F#. Updated the code sample.

# Elixir
[ a, b, c | tail ]
// F#
head::tail
a::b::c::tail // that also works

There are two things worth mentioning while we’re on lists. Pipe operator (|>) works pretty much the same in both languages. In Elixir it binds the first parameter of the function, and in F# last one, but that’s the main difference. It’s a matter of convention and doesn’t really matter in the end. Just worth knowing.
EDIT: as Chris and Paul Blair pointed out, this has a tremendous impact on how currying and partial application works and makes F# much easier in that regard. Check out the comments for details.

The classic approach to lists is that you usually iterate through them with for loop. It’s possible in F#, but Elixir doesn’t have “for” loop. You have to do it in a more functional way, i.e. through recursion. For me, that’s a huge plus on Elixir side, because it forces you to use proper functional approach. In F# for loops are a gateway drug to imperative programming :).

Functions and modules

The first thing that I find annoying in Elixir is that every ‘def’ and ‘defp’ must be paired with ‘end’. It’s like curly braces all over again. Or Visual Basic. It makes code dirty and is excessive. In F#, blocks of code are delimited by the level of whitespace, similar to Python.

In Elixir, functions must be wrapped in Modules. It doesn’t create a big pain, but again – something I don’t have to do in F#. On the other hand, Elixir allows you to do multilevel Modules, which may be convenient in some situations.
EDIT: Anil Mujagic mentioned in the comments, that it also works in F#.

Pattern matching

A bit about Elixir pattern matching was mentioned in the first paragraph. “=” parameter has some impressive qualities. You can also pattern match on function parameters, like shown below in the second example. And you can further simplify it with guards.

# Elixir
# case statement
def blank?(value) do
    case value do
        nil    -> true
        false  -> true
        ""     -> true
        _other -> false
    end
end

# pattern matching on function parameters
def blank?(nil),    do: true
def blank?(false),  do: true
def blank?(""),     do: true
def blank?(_other), do: false

# pattern matching on function parameters with guards
def blank?(value) when value in [nil, false, ""], do: true
def blank?(_other), do: false

In F# it looks similar to the case statement in Elixir. You can also use guards with it and much more.

// F#
let x = 
    match 1 with 
    | 1 -> "a"
    | 2 -> "b"  
    | _ -> "z" 

I couldn’t recreate the same example easily, because of strong typing of F#.  The Same variable cannot have values of different types, and nulls are non-existent in this language. You could have something similar using discriminated unions.

I’m not a fan of Elixir’s approach to this problem with declaring several functions. I prefer F# way again.

Summary

As mentioned in the beginning, I have mixed feelings. For the last couple of years, I’ve been hearing a lot how beautiful Elixir is. And I can imagine for a lot of folks coming from other languages it is. But I’ve been spoiled with F# for last 5 years and I must admit, it’s still my number one. That being said, Elixir lands on the strong second position in terms of beauty. I do appreciate some big uncompromising design decisions that José made to make Elixir much more functional. F# has some “gateway drugs” to imperative programming, as they wanted to leave that option open too and be compatible with the rest of .NET. Big points for Elixir for that. There are some features of F# like discriminated unions or units of measures, that I haven’t found a good replacement in Elixir, but I’m also at the beginning of my journey. I also like F# more for strong typing.

Additional resources

F# has an abundance of operators. Some of them are really crazy. Check this Microsoft document to see all of them.

Quick guides on Elixir and F# syntax. The second one comes from the excellent blog of Scott Wlaschin. If you want to dive into F# more, I highly recommend it.

Next week I’ll be diving into internals. Hopefully, I will find time for that. Come back next week for more Elixir, and if you’re interested in Machine Learning, check my subjective drop of interesting articles in that area.

This post was edited to fix inaccuracies that were pointed out in the comments. Thank you for kind, constructive and informative comments!

DevSum 2015

I’m right now on in Arlanda airport, coming back from DevSum 2015. It was my first DevSum, and it was awesome.
Conference had two days and four tracks. Everything conveniently located in central Stockholm at hotel Clarion Sign. Very close to central station and places for evening activities. The atmosphere was very friendly. I met well known faces from speaker community and made some new friendships. It was most social conference I attended this year, very much similar to how DevDay feels. Most of the speakers didn’t sit in the close “speaker’s lounge”, but mingled with attendees, all led by Tibi, the King of DevSum :).
I didn’t attend many talks, but there were few very intersting. Among them Mark Rendle’s C# 6 talk, Troy Hunt’s and Niall Merrigan’s security talks and Hadi’s “silver bullet” talk. There was also Rob Ashton rant about how Erlang is awesome, but I’m not sure he convinced anybody showing mostly his console scrolling with loads of code and hard to understand error messages flying around. But it was hillarious so that’s ok.
My talk went fairly well. It was another installment of the talk I did at Swettugg and LambdaDays. I had around 30 people on public and I hope they got interested by type providers. Big thanks to Tibi and Cornerstone for this opportunity. Slides and code are on github.

Month of spreading F# love in Poland

In last month or so I did three talks on F# in Poland. I can see gaining interests and there’re already other people speaking about F# in Polish community. This is awesome!

Kraków, 25th September

A Day before DevDay KGD.NET organized meetup with two talks. This was great opportunity for my employer tretton37 to get some more street cred in Poland, so we decided to sponsor some food and drinks. There were two speakers – me and Maciej Aniserowicz, who’s kind of a rock star of Polish .NET community (BTW, check out his new podcast (in Polish)). I did my already well known introduction talk to F#. I had quite a big audience (around 100 people) and they were very engaged. I enjoyed great question and feedback I got after the talk. Looks like it’s very active .NET group. I used the same slides and code as in Warsaw couple months before.

Next dey was a DevDay :). I’m big fan of this conference and it delivered again. There were a lot of semi-negative opinions on the Internet afterwards, which is very sad and unfair. Looks like DevDay became victim of its own success. Last year was fuckin awesome, and people had some overgrown expectations. The truth is, it was fuckin awesome again this time and I can’t wait for next year’s edition. Videos are already online and you can watch them on youtube. But the strongest point of DevDay for me is community impact. It made largely distributed Polish .NET scene more united. People are visiting each other’s group and exchange experiences and knowledge. Programmers from all around Poland know each other better and lot’s of credit for that goes to Michał and Rafał.

Interwebz, 18th October

On Saturday evening I did a talk on Polish virtual conference dotnetconf.pl. From statistics I could see there were about 70 people watching it live. It’s a little bit weird to talk to computer without seeing your audience. I’m not happy how this talk went, but you can judge by yourself, because it’s been recorded (Polish). Feedback I got afterwards kind of matched my expectations – 24 positive, 16 neutral and 2 negative opinions. Again – same slides and code as in Warsaw.

This was the second edition of dotnetconfpl, great initiative by Michał, Paweł and Jakub. It’s Saturday afternoon full of code. Made by Polish developers for Polish developers. And because it was virtual, I could do talk from my desk in Sweden. I also very enjoyed discussions that went on whole day on dedicated jabbr channel.

Poznan, 30th October, PolyConf

Few days ago I did completely new talk. This time about cross-platform mobile development with F# and Xamarin. So this was new talk, and also my first talk in English, and biggest audience so far. Lot’s of new experiences. I was quite nervous before, but seems like everything went well. I’ll see video in a couple of days to make sure, but right now I feel it was my best talk so far.

The conference itself is evolution of well known RuPY. This time they widen topics to other programmic languages, so you could witness talks on JavaScript, Haskell, Erlang or F#. Pretty cool experience, and lot’s of inspiration how to move concept from other technologies to my daily job. The conference, even though it was hosted in Poland, gathered mostly international crowd. I’m putting it on my calendar for next year, because really enjoyed it.

What’s really cool and makes me happy, there’re other people who start talking about F# in Polish community. Few weeks ago my friend Kuba Walinski asked me if he can reference my talk, as he’s gonna do his own about F#. Hell yeah, you can. It’s great that we’re spreading F# love :). He spoke at Developer Days in Wrocław and you can read his thoughts about it on his blog.

There’re some other F# events coming up in Poland, so I’m thinking about starting some kind of Polish Monthly F# news, similar to Sergey’s weekly news, but focusing on our local community. Stay tuned :).

Talking F# in Warsaw

Two weeks ago I had another opportunity to practice my public speaking skills. It took me some time to write this post, because in the meantime I spent few days in Krakow. And Krakow is a different state of mind.

This was another instance of my introductory talk to F#. It went a little better than one on get.net, but still I think there’re things to improve. I got really good feedback from Gutek, who came to see this talk. There were also some other friends from Warsaw – some of them I haven’t seen for years. It was a pleasent surprise.

Warsaw .NET usergroup seems to be similar size to one in Gdansk. There were about 40 people attending. Interesingly, some of them came there for the first time, just because of the topic. Good news that F# is getting some interest in Poland. I got best ever set of question after this session. You could clearly see people are interested and want to know more. Really liked that!

What I didn’t like is that there were no networking activities afterwards. Fortunatelly, there were some friends mentioned before, so we went for some food and drinks. Overally good time, and I’m happy I managed to get there on my way to Kraków.

On the bonus note, I had with me ticket for leetspeak to raffle. Leetspeak is tretton37‘s conference, that we organize every autumn. This year it’s happening on 4th October in Gothenburg. Tickets will be available soon.

WP_20140710_19_41_22_Pro

As usually, slides and demos landed on Github.

There are also good news. I’m doing new F# talk, focused more on cross-platform capabilities. Looks like I will present it on PolyConf and WarmCroc in next few months. I’m excited and terrified at the same time, because they’re gonna be my biggest speaking gigs.

Speaking – “WTF# and why should you care” at get.net conference in Łódź

Nearly two weeks ago I had my first opportunity to speak at a conference. Get.net was organized by Łódź branch of Sii and featured all kinds of talk about .net technologies. Among the speakers you could find many familiar and well known faces from Polish dev scene like Maciej Aniserowicz, Jakub Gutkowski, Basia Fusińska, Michał Śliwoń or Rafał Legiędź. I was humbled and honored to speak in such company.

Speaking at conference isn’t much different than speaking at user group. There were just more people and I had to use microphone. Unfortunately it was the kind of mike you have to hold in your hands and this made live coding quite a challenge. Many other speakers had that issue and I hope organizers will know better next time. Apart from that, conference was quite well organized. Also venue was really nice.

My talk was slightly modified version of one I did for tricity .net group last month. But this didn’t make me feel more confident about it. After all it went quite well and there were even some positive tweets. This is good, right? I hope this sparked some interest for F# in Polish .net community. Overall this was nice experience, and I will actively look for other chances to speak at conferences.

Slides and code are on my github.

BTW, I’m writing this post during Craft Conference in Budapest. I’ll do some writeup next week.

Speaking – “WTF# and why should you care” at Tricity .NET Group meetup

Last week during local .net group meetup I did my first technical talk ever. Well, I did present some stuff on internal meetings in company before, but never for so many people, whom I don’t know.

I was quite nervous before – for many reasons. First of all, I’m not some F# guru. I don’t feel fully entitled to share knowledge about it. I also don’t feel very confident in public speaking situations. But it all come around nicely. I’m generally satisfied how it went.

I’m presenting it again in one month at get.net conference in Łódź, Poland. Based on this experience, I will change few things in this talk. But in general, this was good training.

If you have doubts “should I present something at usergroup”, JUST GO DO IT. But before read Zach Holman’s hints on speaking.io. I found them very useful.

Slides from this presentation are on my github. Code examples I used, were mostly from tryfsharp.org.

Using redis with F# on Windows

In one of my next projects I’ll probably use F# + redis mix. I wanted to try it out, to get some general idea how it will work. I had no previous experience with redis, and I’m still beginner in F#. I wanted to do some end-to-end example for saving and reading data. My idea was to get some Bitcoin price from external service, save it to local redis instance, read it back and chart.

In this blog post, I’ll show how I got there, and what I learned in the process.

Installing redis on Windows

Redis is in-memory key value store. It’s very fast and can store data in few data structures – strings, hashes, lists, sets and sorted sets. Official releases run on linux, but Microsoft Open Tech group developed and maintains experimental port to Windows. And this version I used for my tests.

I simply downloaded code from github, build solution in Visual Studio, and run redis-server.exe from project folder. If you want to test some commands with client, run redis-cli.exe. And if you have no idea, what are the commands try.redis.io has pretty cool interactive tutorial, that cover some basics. Running redis from code build on your dev machine probably is not the best idea for production – I would instead choose to deploy it on some linux server. But for testing purposes it’s perfect.

Getting data from external service

That part was pretty straightforward. I decided to get data from bitstamp.net, because they API for Bitcoin ticker is super easy to use. It has some limitations, but I’ll get to this later. So I made request to https://www.bitstamp.net/api/ticker/ and parsed it using Json type provider from FSharp.Data package (you can install it with Nuget). Json type provider is awesome. After you feed it with some sample data, you have all your fields just “dot” away.

https://gist.github.com/mlusiak/7901990

One thing I learned hard way in this part of code, is that in currentPrice you need those parentheses. Without them, F# will treat the whole block (lines 13 – 15) as calculating value and binding it to currentPrice – not as a function. And because values are immutable by default, it will always “return” the same price.

Saving results to redis

To access redis, I used ServiceStack’s redis client. ServiceStack is great framework to access all kinds of webservices. You can install ServiceStack.redis package using Nuget. It’s free to use up to 20 types.

https://gist.github.com/mlusiak/7902309

You can see three approaches I took (the only difference are first two lines). First one didn’t work – it saved “empty” data (empty strings, integers equal 0, etc.). As Demis Bellot explained to me on StackOverflow, StackService rely on writable properties, which immutable records in F# don’t have. He suggested to use [<CLIMutable>] attribute (which I did in third approach). In between I found this blog post, that used mutable keyword on type fields. This also works, but is not as elegant as the attribute, because it exposes those mutable fields also within your F# code.

Getting data from redis

This was very straightforward. No issues here. It just worked.

https://gist.github.com/mlusiak/7903099

Charting the data

To visualize this data, I used FSharp.Charting library. To make it work, you have to install it with Nuget and reference some libraries like System.Drawing and System.Windows.Forms. I also had to load FSharpCharting.fsx file.

https://gist.github.com/mlusiak/7903123

And it works!

Bitcoin price 11th Dec 2013 around 2am CET

Bitcoin price 11th Dec 2013 around 2am CET

Putting it all together

To summarize – getting data, saving to redis, reading back and charting – all in around 30 lines (excluding referencing libraries) of F#.

https://gist.github.com/mlusiak/7903762

Two more remarks about this code. I call Bitstamp API every 31 seconds, because it gives new data every 30 seconds anyway. If you call it earlier, you’ll get the same data as last time. Second thing is this whole #if INTERACTIVE block. I don’t know why, but when I run code in F# interactive without it, it screamed about no references to libraries. I thought referencing them in project would be enough, but no. And if I wanted to compile and run .fs file, than it failed to compile with #r clauses in it (because .fs file don’t support them, they work only in .fsx files). #if INTERACTIVE allowed me to test code in F# interactive mode, but still compile and run this code as program.

Any comments about code, and way I did things will be appreciated. I’m new to F# world, and I am happy to learn what I could do better.

Some useful references

http://try.redis.io/
http://fsharp.github.io/FSharp.Data/
http://fsharp.github.io/FSharp.Charting/
http://blogs.msdn.com/b/fsharpteam/archive/2012/07/19/more-about-fsharp-3.0-language-features.aspx
http://caxelrud.blogspot.com/2012/11/using-nosqlredis-in-windows-with-f.html

Lots of love for F# during Øredev

Last week I had tons of fun (and learning!) at Øredev conference in Malmö, Sweden. My full writeup is still yet to come, but as videos are popping up, I’d like to show you how well F# and functional programming in general were represented during conference. On second day, you could do a streak of 3 F# talks one after another!

This are links to talk pages, where you can find video (or in some cases not – hope it will pop up soon), grouped by presenters, sorted randomly. Let’s start with F# focused links:

And off to less F#, but still interesting functional talks:

Bodil also gave talk on implementing your own lisp (in Clojure, of course) at nearby Foo Cafe. This was pretty hardcore, and I didn’t get much from it. But it was recorded, so smarter people will probably make use of that.

As you can see, lots of functional love. As always you could always hang out with speakers between/after sessions and ask them (in my case) some lame questions or see them hacking around. Great fun, and good opportunity to learn new stuff.

Progressive F# Tutorials in London

Yesterday I went for a crazy trip to London. At least most people would call that, because for me it was perfect. It had all I like – flying planes, meeting great people and learning new stuff. I woke up at 3 to catch 6 AM flight to London. Then take a train to center, took part in Prog F# Tutorials and then went back to airport to get on 8 PM flight. I was back home around midnight.

Prog F# Tutorials are two day F# conference organized by Skills Matter. In agenda you could find almost all the rock-stars of F# world – Don Syme, Phillip Trelford, Richard Minerich, Rachel Reese, Robert Pickering, Jon Harrop and Simon Cousins.  Unfortunately, I could only attend first day due to medical procedure planned for today, but one day is always better then none.

First talk by Jon Harrop was about adopting F# by large insurance company. He talked about what are best ways to convince people to start using F#, what worked, and what didn’t. I would like this session to be more technical, but there were still few interesting points he mentioned. After that, public split into two rooms. In main one, Rich was live coding (with help of audience) to solve Bank OCR Kata. It was entertaining, and quite interesting to see how someone puts his F# knowledge to solve problems. The other group were solving F# Koans with Rachel Reese. After lunch went to Rachel’s workshop “From Zero to Data Science”. Based on tutorials, you can find on tryfsharp.org, we were “learning by solving” some extra tasks Rachel prepared for us. For beginner like me, some of them were really challenging. Another difficulty proved to be tryfsharp.org’s capacity. Around 100 people trying stuff out there killed the server and it started throwing 503s. Anyway, this was my favorite session of the whole day. In second room Robert Pickering was doing his Undertone session. And to wrap up, Phillip did quick talk about using F# in finance. Unfortunately I didn’t get to see Don Syme’s talk planned for the morning. He got stuck in Germany and didn’t get on time. Bummer, cause I anticipated this one the most.

The whole thing took place in the crypt below old church (this was Halloween! :)). This is so great place to host conference, so different than standard grey rooms. The only problem was, that it was not really wheelchair accessible. But Theo and his Skills Matter crew helped me get there. From logistics point of view everything went pretty great. There were constantly resupplied snacks and coffee, tasty lunch and beer for the end. Wifi worked with some issues, but it hold pretty well, considering over 100 people doing queries against tryfsharp.org.

To sum up – this was a good day. I am okay to travel halfway through Europe to get to events like that. I only wish I could also be there on second day, but maybe next year. I am really happy, that I met in person and talked to some F# pros, whom before that day I only followed on twitter. And Skills matter crew are awesome, and I definitely will look to attend their events in future.

BTW, if you are based in London are into F#, check out this meetup group.