1, 2, 3, Go!

OK, the title is an easy joke, but that's what happens when you give a silly name to a language… So I've started looking at Golang, since it seems to be the newish (ok, ok, not that new) kid on the block. And in fact the name is not an issue: I usually type "golang" to prefix my searches on the web and it works pretty well.

- I installed Go and the first striking thing are the instructions to read "how to write Go code". Having one way to structure the code (one workspace containing source control repositories, each containing packages) makes it very easy to get started - compared say to Java where different IDEs may have different approaches to what a "project" is. I wonder how this structure works when you write Go professionally, and you want to distinguish open sources dependencies from proprietary code. Also coming from Java where you're used to structure classes into packages, seeing Go repositories with a huge number of files inside one folder makes me shudder, but we'll see over time.
- I started of course with the Tour of Go. In a couple of evenings I went through it, proving how easy and small the base language is. Encouraging!
- I then started to get my hands dirty by writing a little app that hooks together JSON web services, Cassandra, Elastic Search and Docker. It was fairly easy to find libraries and manage to put them to use. I'll probably push that code to Github at some stage after some cleaning up.

So Go delivers on the promise to be a language easy to pick up and easy to get started. You can get from zero to productive in a few hours.

These are the features that stood up for me:

- Lack of generics. It's a trope in the computing world "Go doesn't have generics, ha ha ha". Of course straight away you see that arrays/slices and maps are typed, so already the basic use case for generics (safety in collections) is taken care of. Then you have functions as first-class citizens and interfaces, so there are plenty of techniques you can use to go around the lack of generics, so I'm not sure it's such a huge problem.
- Interfaces. It's interesting that there is no explicit declaration that a type implements an interface. If you define a Duck interface with a Quack method, every type that you use as the receiver for an implementation of a Quack function is considered a Duck. This is nice, but still tooling support to find out all types that implement a given interface will be a must ("OK, this function expects anything implementing Duck, what implementation can I use?").
- Pointers. I'm at the core a Java developer, so the idea of pointers makes me a bit uneasy. But I breathed easier when I saw "no pointer arithmetic". In fact, pointers in Go just make explicit if you pass a struct by value or by reference. I feel this adds a level of clarity that is worth the extra syntax and the initial repulsion the word "pointer" may awake in some.
- Errors. Go recommends a style where a function that may fail should return a tuple: normal value, error. The calling code can decide to ignore the error or deal with it. This is reminiscent of Either in Haskell. I'm still not sold that this is a better system than checked exceptions (but I seem to be the only one liking checked exceptions it seems), but I'll need more practice before I make my mind up.

So all in all I like a lot of design decisions that were made in Go, and it certainly makes for a pleasant programming experience. I ran into a few gotchas that I'll cover maybe in later posts, but nothing too stressful. So far, I have to say I enjoyed the experience!

Happy Go Hacking!

A little RPG in React Native

I built a little role-playing game in React Native. I tried to build the type of game I like playing, with quests and interactions with non-playing characters, while learning some mobile UI programming tricks.  These are some of the main points that I took away:

• The initial setup was a bit involved, probably because I'm not used to develop JavaScript applications. Getting the right code to properly do the plumbing between React, Redux,  React Navigation, tests, etc. was a bit of a hassle. Obviously this has to be done once and then you can concentrate on writing the functional code. As I noted recently, then upgrading to newer versions of your dependencies can be a hassle!
• I was happy with my declarative approach to the game world. I don't think it would be manageable to do otherwise.  I define as JavaScript structures the world itself: the different places and how they communicate, the items they contain, etc., the non-playing characters and the possible interactions you can have with them, items and their characteristics, monsters and spells. This gives me an immutable representation of the start world, and the state of an actual game just has to store the modifications from that initial state
• This of course could mean that I (or somebody else) could reuse the game mechanics for a totally different adventure!
• I of course used of Redux to manage state. The state is only modified by Redux reducers, so everything the player does in the UI just becomes actions, not explicit state management operations. I combine several reducers, each reducer being responsible for modifying one section of the global state, which makes each reducer simpler, but fragment the code. For example when the player takes an item from a room, one reducer adds the item to the inventory, another removes the item from the room, so maybe there's some potential for bugs there
• I found the integration between React and Redux easy to use: you simply define the mapping between the state and components properties, and between component interactions and Redux actions.
• I abused a little bit Redux to implement combat: combat holds a kind a mini state for each fighting round, and then the result of a fighting round both is represented in the UI ("the rats bite you for 2 damage"), and impacts the global world.
• I didn't spend too much time on the UI, just using basic React Native components. I found some of the layout hard to do correctly, and styling components is not intuitive when you're not a CSS expert. Maybe I should take a CSS/Design course, because you can tell from my UI designs that I'm a programmer :-)
• All in all, writing in modern JavaScript was nicer than expected, even though I think using a stronger typed language would be better. If I had to do another similar project I would probably try to use Typescript. I liked especially the object spreads to update parts of structures and the use of consts.
• I used Expo to test on a tablet, I didn't try to actually generate a final application outside of Expo, I haven't looked at all on how to distribute the game as an app.

All in all, if was an enjoyable experience, but of course designing a full game instead of just a prologue you can do in 5 minutes would be a different type of endeavor...

Fun with NPM and Expo

Some time ago, I wrote a little game using React-Native so I could play around in Javascript with React, Mobile development and Redux. Yesterday I checked this project again on Github, and saw that there was a security issue Github detected and warned me about: the "merge" library had a vulnerability, reported in CVE-2018-16469. OK, time for action!
Of course, my project doesn't reference merge directly. It's a transitive dependency of jest. A quick check on the web showed that since I created the project, a lot of things have happened, so my project dependencies are lagging behind. So hopefully upgrading should solve my security issue.
I find instructions at https://stackoverflow.com/questions/16073603/how-do-i-update-each-dependency-in-package-json-to-the-latest-version, so I run npm outdated, which indeed confirms a lot of my dependencies are old.
I install npm-check-updates:
npm i -g npm-check-updates
ncu -u
As indicated, and I get:
Hmmmmm... this is taking a long time. Your console is telling me to wait for input on stdin, but maybe that is not what you want.
Try specifying a package file explicitly with --packageFile package.json.
See https://github.com/tjunnone/npm-check-updates/issues/136#issuecomment-155721102

OK, then:
ncu -u --packageFile package.json

This updates everything, and then my app doesn't start anymore. Turns out a lot more changes have happened when I wasn't looking, and the react native starter app I created has now changed to use expo-cli. I find some instructions on how to change the npm scripts, but it doesn't solve everthing, I still get an error in the react-native-scripts main file, because the main entry also needs to be changed (thanks https://docs.expo.io/versions/latest/sdk/register-root-component#i-created-my-project-before-sdk-18). Then it stills fails because the babel module has been renamed, thanks to https://forums.expo.io/t/problem-upgrading-to-sdk-31-cannot-find-babel-plugin-transform-react-jsx-source/16246. And then on my expo client I get a Javascript mismatch error, that https://stackoverflow.com/questions/47763824/react-native-version-mismatch helped me solve...

OK, now my game starts again, I suppose I need to test it thoroughly because something may again decide to break... I did enjoy developing the game, but certainly managing the NPM vulnerabilities and the Javascript ecosystem pace of change can be challenging. I know this isn't an original thought, but experiencing it first hand is definitely an eye-opener!

Reboot

Whoa, nearly two years since I last put something on this blog. I lost the habit, and since I'm not involved in EclipseFP anymore I don't have the stream of Haskell news to report I used to. I will now try to reboot it and try to find interesting experiences to share!

I was never a big fan of social media sites, but I use to link to some of these blog posts on Google +, which is now dying. So this should stay a simple blog, where I have nothing to sell you and no ads to pester you with!

Over the last few months I've built a toy project in React Native, started learning Go, and done a lot of things in my day job, so hopefully some interesting stories will appear! Stay tuned!