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I am trying to learn ReactiveX. I have spent almost a whole day and I am not able to understand it properly. I tried to look the official documentation but is is very difficult to understand. Something like this:
"Rx.Observable.prototype.flatMapLatest(selector, [thisArg])
Projects each element of an observable sequence into a new sequence of observable sequences by incorporating the element's index and then transforms an observable sequence of observable sequences into an observable sequence producing values only from the most recent observable sequence."
How a new person is able to understand it. So if someone knows the good resource then please mention
As a commenter has said, Brian Troncone's page is a good place: https://www.learnrxjs.io/.
The reality is that learning Rx is not a snap. The hard part isn't learning the library, the operators, etc. Rx requires at least a little bit of investment in thinking differently, at least for most people (myself included).
The best way to start understanding it is to play with it. For RxJS, the interactive examples in rx-book are a great place to start. They use jsbin, so you can run the sample code to see the output, then tweak the code to see what difference it makes.
From a .Net angle, playing with Linqpad is the best way to start getting a feel for how Rx works.
Ultimately you'll need to combine different aspects of learning:
Some theory reading
Some practical examples (which is where rx-book is useful)
Some practical application to a demo or real system of your own
I have a list of helpful resources that I've compiled here. But there is so much being put out there, especially on rxjs, that it's hard to keep up.
What's not common is true examples of real world usage of Rx. Partly this is because Rx is typically applied to larger scale problems, so it's not easy to just fabricate a good use case to make a demo from.
ReactiveTrader is one example of a large scale demonstration of applying Rx. It's a good example of an app making heavy use of Rx to build a complex web app that deals with streaming data and UI events.
I've also given a talk on how to apply Rx to tweet streams to analyze the data. This is oriented around real-time manipulation, aggregation and filtering of streaming data. There's a full video of the talk, plus articles discussing the approach and results here.
Ultimately it will take you time to learn Rx, but it will be worth the effort if you follow through.
The best way to learn RxJs to play with it by going through the api reference.
Besides that you can go through the following resources:
Video courses on Egghead.io
Awesome explanation: The introduction to Reactive Programming
you've been missing
Hot vs Cold Observables ( Also All Ben Lesh Articles on Medium)
Tutorials on youtube like : Adding Even More Fun to Functional
Programming With RXJS - Ryan Anklam
Explanatory tutorial with example on
https://auth0.com/blog/understanding-reactive-programming-and-rxjs/
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As a student I have many languages/technologies to learn. Many times I forget past languages within 2-3 years unless I am practicing them on a regular basis.
Suppose on a later date, you have to remember it again. You have to almost start from basic & revise it. Isn't there a better way to retain all the things I learnt?
Live Example: As a student I have to learn C++, JS, Vbscript, Bash, and later on Java and C#/.NET. My side projects are also in PHP.
All these are different in their syntaxes, number of features & quirky inner details.
Especially in C++ & Java there are so many inner details that must be remembered. Like initialising base class pointers with derived class object, different ways of casting in C++, and so many more that are so different from any other language.
Forgetting all this in 2 years is just a huge loss.
How do you remember all these different languages and technologies?
P.S: I had one idea of a quick reference sheet. Does anyone have any experience of creating one? Is there any place where I can get them? What are the other ideas?
It's all repetition really. You'll be doing a lot of it and you'll eventually get used to it. Languages that are very similar, like Java and C#, can be a bit confusing at times, but that's where code-completion comes in handy.
You'll get used to it eventually. And every programmer who has to work with many different languages always needs to refresh him/herself after not doing a particular language in a while. There are no exceptions there.
Don't be put off by tutorials you find online, or blogs with loads of examples. The people that post those work several days, maybe even weeks on a single post. They're not super-geniuses who sit down, write their article in 30 minute and post it. Much preparation goes in to those things. In fact, most blogs that have a high turnout, have multiple people working on it. But their names are always in tiny print somewhere at the top or bottom so I always missed that. I know I used to assume these people were just that talented that they could come up with a big idea and write it out in a couple of hours. And many people who were in college with me also thought this. It all seemed so grand and frankly, it was a bit depressing. The idea that we would one day become that good seemed so far away that many people I knew in college just gave up.
Don't be put off by the magnitude of it all. You'll get used to it if you do it enough. Don't pay attention to those books you see in stores or online that say "Java expert in 24 hours". Realistically speaking, count on 5-7 years to become good at a certain language.
Googling "Java Cheat Sheet" and "C++ Cheat Sheet" will turn up some pretty good ones as a starting point. Making your own is a better option though, improve on it as you go and you'll come out with something you're familiar with and excludes things you don't need.
Over time you'll probably get over this problem but a quick reference sheet never hurts.
Get Cheat sheets of each programming language or libraries
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Are there any programming methodologies that take into account the concept that the first round of written code is likely to be not what you want to use? The most common thing I hear at the end of a project from a developer is 'If I could do that again, I'd do it so differently.' This is almost an exact mirror of the process a writer goes through after writing a first draft. The difference seems to be that writers then rewrite and rewrite again until they're ready to move into the editing stage, whereas developers seem to write and then refine their first draft with testing and refactoring.
I'm certainly no fan of trying to use alternative analogies to define the development process, but I do think there's value in recognising that your first draft is just to get ideas down, you need further rewrites in order to produce something worthwhile. I just don't think I've ever encountered a programming process or project methodology that recognises that, so I was hoping that the vast collective concious of Stackoverflow might have an idea of where I might start exploring this possibility?
Prototyping seems to address the problem in some way. The wikipedia article on Prototyping names an approach called 'Throwaway prototyping' which seems inline with your way of thinking.
What you are describing is called throwaway prototyping. The idea is that as soon as you have your preliminary requirements, you create a basic model of the system to show the user and/or customer what the final system might look like and how it might function (although there's no real functionality). The user provides feedback on this prototype.
If you wanted to utilize throwaway prototyping, my first suggestion would be to start looking at the spiral process model. However, I'm not familiar with very many methodologies that explicitly utilize throwaway prototyping. The more "agile" methodologies favor evolutionary prototyping or incremental prototyping. The only time I've ever personally used throwaway prototyping was to only prototype the user interface, as the underlying system was already under development and I used whiteboards and pen and paper for the prototypes.
Besides, this is one of Brooks's ideas which he himself found not the most effective after some revision: you've probably heard of "throwing away two systems after planning to throw away just one". Fortunately many such troubles can be overcome nowadays thanks to agile methodologies.
This is exactly the argument that Bruce Eckel is making here.
I would argue that the best thing to do is modularize very well. For example, if you're writing a kernel, the "Get the next available free memory frame" function should reside in its own function. That way, when you figure out that it's written in a really crappy way, you simple erase (of course you're using version control) and start from scratch. That way, your existing modules exist as a way to test your new code.
Going from start to finish and then start to finish again is an awesome way of going through a large percentage of the same bugs again.
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I'm working on a quite large project, a few years in the making, at a pretty large company, and I'm taking on the task of driving toward better overall code quality.
I was wondering what kind of metrics you would use to measure quality and complexity in this context. I'm not looking for absolute measures, but a series of items which could be improved over time. Given that this is a bit of a macro-operation across hundreds of projects (I've seen some questions asked about much smaller projects), I'm looking for something more automatable and holistic.
So far, I have a list that looks like this:
Code coverage percentage during full-functional tests
Recurrance of BVT failures
Dependency graph/score, based on some tool like nDepend
Number of build warnings
Number of FxCop/StyleCop warnings found/supressed
Number of "catch" statements
Number of manual deployment steps
Number of projects
Percentage of code/projects that's "dead", as in, not referenced anywhere
Number of WTF's during code reviews
Total lines of code, maybe broken down by tier
You should organize your work around the six major software quality characteristics: functionality, reliability, usability, efficiency, maintainability, and portability. I've put a diagram online that describes these characteristics. Then, for each characteristic decide the most important metrics you want and are able to track. For example, some metrics, like those of Chidamber and Kemerer are suitable for object-oriented software, others, like cyclomatic complexity are more general-purpose.
Cyclomatic complexity is a decent "quality" metric. I'm sure developers could find a way to "game" it if it were the only metric, though! :)
And then there's the C.R.A.P. metric...
P.S. NDepend has about ten billion metrics, so that might be worth looking at. See also CodeMetrics for Reflector.
D'oh! I just noticed that you already mentioned NDepend.
Number of reported bugs would be interesting to track, too...
If your taking on the task of driving toward better overall code quality. You might take a look at:
How many open issues do you currently have and how long do they take to resolve?
What process to you have in place to gather requirements?
Does your staff follow best practices?
Do you have sop's defined to describing your companies programming methodology.
When you have a number of developers involved in a large project everyone has their way of programming. Each style of programming solve the problem but some answers may be less efficient than others.
How do you utlize you staff when attacking a new feature or fixing the exist code. Having developers work in teams following programming sop's forces everyone to be a better code.
When your people code more efficiently following rule you development time should get quicker.
You can get all the metrics you want but I say first you have to see how things are being done:
What are you development practices?
Without know how things are currently being done you can get all the metrics you want but you'll never see any improvemenet.
Amount of software cloning/duplicate code, less is obviously better. (Link discusses clones and various techniques to detect/measure them.)
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A couple of weeks ago, my piano teacher and I were bouncing ideas off of each other concerning meta-composing music software. The idea was this:
There is a system taking midi input from a bunch of instruments, and pushes output to the speakers and lights. The software running on this system analyzes the midi data it's getting, and determines which sounds to use, based on triggers set up by the composer (when I play an F7 chord 3 times within 2 seconds, switch from the harpsichord sound to the piano sound), pedals, or actual real-time analysis of the music. It would control the lights based on the performance and sounds of the instruments in a similar fashion - the musician would only have to vaguely specify what they wanted - and real time analysis of their playing would do the rest. On the fly procedurally generated music could play along with the musician as well. Essentially, the software would play along with the performer, with one guiding the other. I imagine that it would take some practice to get use to such a system, but that it could have quite incredible results.
I'm a big fan of improv jazz. One characteristic of improv that is lacking from other art forms is the temporalness of it. A painting can be appreciated 10 or 1000 years after it has been painted, but music (especially extemporized music) is about the performance as it is the creation. I think that the software that I described would add a great deal to the performance, as with it, as playing the exact same piece would result in a completely different show each time.
So, now for the questions.
Am I crazy?
Does software to do any or all of this exist yet? I've done some research and haven't turned up anything. The key to this system is that it is running during the performance.
Were I to write something like this, would a scripting language such as Python be fast enough to do the computations that I need? Presumably it'd be running on a fairly quick system, and could take advantage of the 2^n core processors Intel keeps releasing.
Can any of you share your experience and advice concerning interfacing with musical instruments and lights and the like?
Have any ideas or suggestions? Cold and harsh criticism?
Thanks for your time in reading this, and for any and all advice!
(And sorry for the joke in the tags, I couldn't resist.)
People have used Max MSP to do this kind of thing with Midi and creating video accompaniment, or just Midi accompaniment. It's a completely domain specific app, that probably was inspired by small talk or something, which barely any real programmer could love, but musician-programmers do.
Despite the text on the site I just linked to, and the fact that 'everyone' uses the commercial version, it wasn't always a commercial product. Ircam eventually released it's own lineage. It's called jMax. PureData, mentioned in another post here is another rewrite of that lineage.
There's also CSound; which wasn't meant to be real-time, but is likely able to be pretty real-time now that you have a decent computer compared to where CSound started.
Some people have also hacked Macromedia Director extensions to allow for doing midi stuff in Lingo... That's very outdated, and hence some of them have moved to more modern Adobe environments.
Look at PureData. It can do extensive midi analysis and folks use it for performance.
Indeed, here's a video that flashes past a puredata screen. It shows someone interacting with a rather complex instrument using PD.
Also, look at CSounds.
I have used PyAudio quite extensively for dealing with raw audio inputs, and found it to be very unpythonic, acting much more like a very thin wrapper over C code. However, if you're dealing with midi, rather then raw waveforms, then your tasks are quite a bit simpler, and python should be quite fast enough, unless you play at 10000 beats per minute :)
Some of the issues: detecting simultaneity, harmonic (formal - i.e., chord structure) analysis.
This is also an 80/20 problem that if you restrict the chord progressions allowed, then it becomes quite a bit simpler. After all, what does "playing along" mean, anyway, right?
(Also, at electronic music conf's I've been too, there are lots of people doing various real-time accompaniment experiments based on input sound and movement). Good luck!
You might also look at ChucK and SuperCollider, the two most popular 'real' realtime music programming languages.
Also, you might be surprised at how much you can accomplish with Ableton Live racks.
(and it's CSound. No 's' at the end)
see also:
Keykit
Arx
I have no idea if the second one is actually real or worth looking at. Keykit, however, is.
You might contact Gary Lee Nelson in the TIMARA department at Oberlin. 20 years ago I did a project that auto-generated the rhythm section for 12 bar blues and I recall him describing a tool that he knew of that did essentially what you're describing.
You might be interested in GenJam
The answer to your question is no - you're not crazy.
Similar systems exist, but your description is pretty
vague to begin with so it's not much of a spec to judge against.
I suggest you start writing a prototype and see how it does.
Something extremely small and simple.
Existing systems be damned.
I'm using c++ on win32 api (no mfc).
Started writing my sequencer back on the Amiga500.
It doesn't do lights, but there's plenty to do in just music.
Good luck to you.
It's an EXTREMELY fun project.
I'd say -don't- pattern your project on how other projects work.
Because, if you ask me, they don't work so great ;)
And the fun is being able to do something different.
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So basically I am looking for good templates for writing both technical and functional specs on a project or work request.
What do you use? How deep do you get while writing the specs? Any additional general tips you could provide would be appreciated.
My company needs these badly. I work for a contractor and right now we do not use these documents at all.
EDIT: I have read Joel's take about Painless Specification, I really liked it, but are there any other opinions :)
On general tips;
We are implementing a process of
1) Business Requirements Statement (BRS)
2) Functional Specification
3) Technical specification
The BRS covers what the business problems are, and what the requirements are around solutions, testing, security, reliability and delivery. This defines what would make a successful solution.
The functional spec details what is needed, how it should look, how long fields should be, etc.
The technical spec details where the data comes from, any tricky code that may need to be considered.
The customer owns the requirements. The developers own the tech specs, and the functional spec is a middle ground. Testing is done against the tech specs (usually unit testing) then against the functional specs (usually system testing) and then against the requirements (UAT).
The important part of this (and we are struggling with) is that the developers still need to deliver to the functional spec, and the original business requirements. In reality the functional and tech specs are just there for clarity.
In short, my main tip is to first work out the process you wish to implement. Then seek agreement from all parties involved in your proposed process, then work on the templates to fit. The templates themselves are only are a small part of the change you want to make.
Not a template, but Joel has written a couple of articles on writing a functional spec. He also has sample here.
You can buy templates from ieee and other places, but I have always ended up making my own.
For a technical spec, "Code Complete" by Steve McDonnell has a good checklist, you can draw some info from that. At my last job, I just made a template out of his section headers, and tweaked it from there.
As far as a functional spec, the important thing is to define all the interfaces:
UI (screen mockups)
Software interfaces (plugins, etc.)
Hardware interfaces (if appropriate)
Communications interfaces (Services, email, messaging, etc.)
There should also be a section for business rules, things that are important functionally that are not covered in any interface definition.
If you want to purchase a book, Software Requirements by Karl Wiegers has templates for a few documents as an appendix. Unfortunately, I'm at work and that particular book is at home. If someone has it handy, they might be able to confirm that.
I happen to like this one, among others: ReadySet.
He sells a pro version too.
This is the best one I have found: http://www.jiludwig.com/templates/FRDTemplate.doc
Start off simple, and work your way from there. Since this is your first experience working with this, use a word document with bullet points. Write it, re-read it and provide enough detail that it makes sense. For technical specifications, you may want to lead the developer toward a solution, but for functional specifications the "how" should be completely missing.
I would suggest to have a look at the Roberston's Volere template here. They are part of the Atlantic Systems Guild, together with people like Tom DeMarco and Timothy Lister of "Peopleware" fame.
As the template is copyrighted, I will not reproduce it here, but give you some of the main headers:
The Purpose of the Project
The Stakeholders
Mandated Constraints
Naming Conventions and Terminology
Relevant Facts and Assumptions
The Scope of the Work
Business Data Model and Data Dictionary
The Scope of the Product
Functional Requirements
Look and Feels Requirements
...
There are many more, but this should give you an idea. The most interesting part of the template is the requirements shell that lists functional requirements on a kind of cue card. Again copyrighted, but truly valuable.
Look here in chapter 9.