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a little question in which I hope you can help me. (To make my life simpler)
One of the most respected numerical solvers for differential equations is LSODA, however it is written in Fortran... ( http://www.netlib.org/odepack/index.html )
There does not seem to be a decent solver for C#, and writing my own is too time consuming in C#, especially as I have very stiff equations that need to be solved.
The NAG libraries for net do not contain an ODE solver (they lack D02 routines). In terms of "university side" libraries that's it.
However NAG Support suggested calling their dll, which is fine for simple variables, but has me rather perplexed with its external functions and dummy parameters which made me give up.
This leaves LSODA still, which is fortran, but a lot simpler in its calling sequence - so I wonder, how can the Odepack (the solvers that include the lsoda routine) be turned into a dll with little work, so that it may be called from C#?
(Which will leave me worried about the Jacobian, being a matrix, i.e. 2D array.)
Specifically, I would like a situation similar to that with the Fortran NAG library, but instead offering me access to lsoda: http://www.nag.co.uk/numeric/csharpinfo.asp
Please keep in mind that I am a mathematician - so if your responses loose me, please be patient with me. And why am I so focused on C# - well, it is simple, especially when one has VisualStudio 2010.
Many thanks for any responses in advance.
SmartMathLibrary looks dead, but it claims to have ODEPACK bindings. You could also check out Wikipedia's List of .NET Numerical Packages.
If you're open to other languages, Python's SciPy library contains a binding to LSODA: enter link description here. It's available on Windows, easy to use, free, and widely embraced by the scientific community.
It's not a full solution, but f2c (Fortran-to-C converter) should be able to give you working C code from the Fortran source. That might at least be easier to get working from C#.
Disclaimer: I've never used f2c to convert a routine, I've only used some of the routines that someone else converted.
I may be starting a new job which requires VB.NET but I am a C# developer and even though I may be able to understand the code, writing it from scratch seems to be a hassle for me for a while.
There are C#>VB.NET converter out there (online) and where you paste your C# code and it converts it into VB.NET code. My question is whether there is any person who experienced this and whether it is a good temp solution or I am gonna experience so much difficulties with that? Do they convert good?
And probably I am gonna run the codes on Asp.net.
An example converter: http://www.developerfusion.com/tools/convert/csharp-to-vb/
Thanks in advance.
Don't use converters - learn VB.NET and the differences between its syntax and C#.
There is a very good comparison cheat sheet here to get you started.
In practice, you will find that most of the time you are interacting with familiar .NET objects in the same way and you only have some syntax differences (though generics and delegate syntax are such a pain that one tends to shy away from them).
Microsoft has stated that they are trying to bring both language to feature parity, so anything you can do in C#, you should be able to do with VB.NET (with minor differences normally).
Update - don't forget that compiled code (in assemblies) should work identically in both languages (assuming CLS compliance), so you could write a library in C# for use with VB.NET and vice versa.
You can try the Telerik Code Converter
That being said, it would be a valuable exercise to convert the code manually. You'll gain a good amount of experience by doing a manual conversion and you'll learn some of the key differences between the 2 languages that may help you going forward.
I'd say your code will work, but you'll miss some special features for which there is no C# equivalent and which would make your code fit better with the language. Some examples:
In C#, you assign event handlers with +=, which will be translated to AddHandler. In VB, however, it's much more common to use WithEvents instance variables. This is especially relevant for ASP.NET, where C# often uses the AutoEventWireup feature, which done in VB through WithEvents instead.
In C#, you access XML through LINQ to XML method calls, which will be translated to the matching method calls in VB. However, in VB, it's more natural to use the integrated language support for XML.
This is good for converting the bulk of your code, but it's not a total solution. One thing you will have issues with is the converter knowing what to do with C#'s indexer brackets ([]) vs. method parentheses (()). VB uses parenthesis for indexers and methods and there's no way for it to know which to use.
I've gone through conversion hell with these things and finally decided that they were just too much trouble and that it was much easier to just convert it by hand. I come from a VB background, so this wasn't a huge deal for me.
For what you want to do, though, you need to learn VB.NET syntax. Writing everything in C# and converting it to VB.NET is not a good, long-term solution. You will eventually have to learn VB.NET. Your manager(s) will not be keen to the fact that you're not learning the core fundamentals of the language you were hire to program in.
Don't do it... There are converters, but you will find that once you learn the key differences that you will be fine. You will interact with the .NET libraries in the same way so much of the programming will be the same.
I just changed jobs recently and went the opposite direction. I'm glad I took the time to learn C#. Major dividends in the end and you'll be more versatile.
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For someone who’s been happily programming in C# for quite some time now and planning to learn a new language I find the Python community more closely knit than many others.
Personally dynamic typing puts me off, but I am fascinated by the way the Python community rallies around it. There are a lot of other things I expect I would miss in Python (LINQ, expression trees, etc.)
What are the good things about Python that developers love? Stuff that’ll excite me more than C#.
For me its the flexibility and elegance, but there are a handful of things I wish could be pulled in from other languages though (better threading, more robust expressions).
In typical I can write a little bit of code in python and do a lot more than the same amount of lines in many other languages. Also, in python code form is of utmost importance and the syntax lends its self to highly readable, clean looking code. That of course helps out with maintenance.
I love having a command line interpreter that I can quickly prototype an algorithm in rather than having to start up a new project, code, compile, test, repeat. Not to mention the fact I can use it to help me automate my server maintenance as well (I double as a SA for my company).
The last thing that comes to mind immediately is the vast amounts of libraries. There are a lot of things already solved out there, the built-in library has a lot to offer, and the third party ones are many times very good (not always though).
Being able to type in some code and get the result back immediately.
(Disclaimer: I use both C# and Python regularly, and I think both have their good and bad points.)
I'm primarily .NET developer and using Python for me personal projects.
What are the good things about python that developers love?
I can say for myself - Python is like a breath of fresh air.
1) It's simple to learn, took about a week for me in the evenings. I'm saying about Python + Django. Python syntax is quite simple.
2) It's simple to use. No troubles installing Python + Django on Windows at all.
3) It can be run on Windows and UNIX.
4) I need it for web, so I get cheaper hosting than ASP.NET.
5) All the advantages of Python language over C#. Like tuples - so useful!
The only thing I don't like is that my favorite IDE Visual Studio doesn't support it (I know about IronPython, don't you worry).
I'm a very heavy user of both C# and Python; I've built very complicated applications in both languages, and I've also embedded Python scripting in my major C# application. I'm not using either to do much in the way of web work right now, but other than that I feel like I'm pretty qualified to answer the question.
The things about Python that excite me, in particular:
The deep integration of generators into the language. This was the first thing that made me realize that I needed to take a long, serious look at Python. My appreciation for this has deepened considerably since I've become conversant with the itertools module, which looks like a nifty set of tools but is in fact a new way of life.
The coupling of dynamic typing and the fact that everything's an object makes pretty sophisticated techniques extremely simple to implement. It's so easy to replace logic with tables in Python (e.g. o = class_map[k]() instead of if k='foo': o = Foo()) that it becomes a basic technique. It's so normal in Python to write methods that take methods as parameters that you don't raise an eyebrow when you see d = defaultdict(list).
zip, and the methods that are designed with it in mind. It takes a while before you can intuitively grasp what dict(zip(k, v)) and d.update(zip(k, v)) are doing, but it's a paradigm-shifting moment when you get there. An entire universe of uninteresting and potentially error-laden code eliminated, just by using one function. Then you start designing functions and classes with the expectation that they'll be used in conjunction with zip, and suddenly your code gets simpler and easier. (Protip: Or itertools.izip. Or itertools.izip_longest.)
Speaking of dictionaries, the way that they're deeply integrated into the language. Understanding what a line of code like self.__dict__.update(**kwargs) does is another one of those paradigm-shifting moments.
List comprehensions and generator expressions, of course.
Inexpensive exceptions.
An interactive intepreter.
Function decorators.
IronPython, which is so much simpler to use than we have any right to expect.
And that's without even getting into the remarkable array of functionality in the standard modules, or the ridiculous bounty of third-party tools like BeautifulSoup or SQL Alchemy or Pylons.
One of the most direct benefits that I've gotten from getting deeply into Python is that it has greatly improved my C# code. I could generally understand code that had a variable of type Dictionary<string, Action<Foo>> in it, but it didn't seem natural to write it. (I use static dictionaries to replace hard-coded logic far more frequently today than I did a year ago.) I have no difficulty understanding what LINQ is doing now, or how IEnumerable<T> and return yield work.
So what don't I like about Python?
Dynamic typing really limits what you can do with static code analysis. Not only isn't there a tool like Resharper for Python, in a language where it's possible to write getattr(x, y)() there really can't be.
It has a bunch of inelegant conventions. How I would love to be able to go back in time and try to talk GVR out of the idea that lambda expressions should be introduced with the word lambda - it's pretty damning that something as fundamental as lambda expressions should be more concise in C# than they are in Python. The leading and trailing double-underscore convention is horrible, and the fact that people mutely acquiesce to it is testimony to Dostoevsky's observation that man is the animal who can get used to anything. And don't get me started on the fact that a module with the name of StringIO was allowed to get out the door.
Some of the features that make Python work on multiple platforms also make it kind of baffling. It's easy to use import, but it's really not easy to understand what the hell it's actually doing. (Where is it looking? What does __init__.py do? Etc.)
The amazingly rich library of standard modules is so amazingly rich that it's hard to know what's in it. It's often easier to write a function than it is to find out whether or not there's something in the standard library that does the same thing - I'm looking at you, itertools.chain.
Your question is kind of like a plumber asking why carpenters are always going on and on about hammers. After all the plumber doesn't have a hammer and has never missed it. Python (even IronPython) and C# target different types of developers and different types of programs. I am very comfortable in Python and enjoy the freedom to focus on the business rules without being distracted by the syntax requirements of the language. On the other hand I have written some fairly substantial code in C# and would be very concerned about the lack of type safety had I taken on the same task in Python. This is not to say that Python is a "toy" language. You can (and people have) write a complete medium or large application in Python. You have the freedom of dynamic typing, but you also have the responsibility to keep it all straight (frameworks help here). Similarly you can write a small application in C#, but you will bring along some overhead you do not likely need.
So if the problem is a nail use a hammer, if the problem is a screw use a screw driver. In other words spend some time to learn Python, get to know it's streangths (text processing, quick coding cycles, simple clean code, etc) and then when you are looking at tackling a new problem ask whether you would be better off in Python or C#. One thing is certain. So long as C# is the only programming language you know, it is the only one you will ever use.
Pat O
My language of choice is C#, and I didn't quite see the point for me to learn Python so far. This talk from PDC09 really piqued my interest: the guy demonstrates how you can use IronPython (or IronRuby) to make a C# app scriptable (in his demo, drop a Python script in a text box, and it works with/extends your C# code). I found this really fascinating: I don't even know where I would start to do something similar in C#, and this made me at least appreciate that it brings something different to the table, which could really enrich what I can develop!
I'm an asymmetrical user of both languages, in a sense that I use C# mostly professionally and Python for all my "fun" projects (not that work is never fun, but... you know...)
This difference of context may skew my perspective, including my opinion that they are two distinct types (pun intended) of languages for, generally, distinct purposes.
This said, it may not be a coincidence that Python is, at this point in time, [one of?] the languages of choice for all kinds of cutting edge, somewhat scholarly, technology/science oriented projects. (And BTW, this "scholarly" keyword here doesNOT imply, that Python is a university toy, plenty of "serious" applications in plenty of domains/industry are proof to the contrary). This may be due to several factors:
(I don't develop most points, readily well expressed in other responses)
the openness and quasi universal availability of Python (unlike C# !)
the lightweight / ease of use / low learning curve
the extensive, high quality, "standard" library and the extensiver (and occasionally bum quality, but on the whole available, open-sourced, etc.) additional library.
the wide array of open source projects in Python language
the relative ease to bind with C/C++ for reusing legacy code, but also for placing performance-critical portions of a project
the generally higher level of abstraction of may constructs of the language
the multi-paradigms (imperative, object oriented and functional)
the availability of practitioners in so many domain of science and technology
and, yes, the
"herd mentality effect" mentioned in a remark, possibly in a [self?] deriding way. The fact that a language attracts a broad, "closely knit" community, makes it attractive too, beyond the superficial ("look cool" and such) traits of herd mentality. Put in broader context, sometimes the best technology/language to use is not measured on the its intrinsic merits but on the overall "picture", including the user community.
I like all stuff with [] and {}. Selectors like this [-1:1]. Possibility to write less code, but more something meaningfull, that gives to write Models and other declarative things very DRY.
Like any programming language, it is just a tool in the box or a brush by which you may paint your creation. Any creative endeavour requires that the artist loves the tools he uses; otherwise, the outcome suffers. Some people like Python for the same reason others love Perl. Incidentally, I have found that most Python lovers loathe Perl's flexible and expressive syntax. As a Perl lover, I don't hate Python, but consider it to be overly structured and restrictive.
If you ask me, all of these throngs of people who seem to love Python were silently suffering under the tool choices before Python came into being. Some suffered under Perl, others under something else. In other words, I believe that when Python came along, it found a large group of silent sufferers longing for a tool like Python.
I can't program in Python because I can't "think" in Python. I can "think" in Perl, therefore, it is the tool I prefer. The silently suffering mass of, now, Python users seem to have found some long lost salvation. Now if they could only keep their evangelism to themselves :).
If you are familiar with the .NET CLR and prefer a statically-typed language, but you like Python's lightweight syntax, then perhaps Boo is the language for you.
Don't get me wrong, I am and will always be a devoted fan of C#.
But sometimes there are things I can't do in C#. lthough C# keeps reducing those gaps, Python is still the language I go to to fill them.
It's dynamic, flexible, powerful, and clean. Lovely language. Whenever I need to script or build dynamic or functional (as in functional programming) software, I go Python.
For me Python is the most elegant language I've used. The syntax is minimalist (significantly less punctuation than most) and intentionally modeled after the psuedo-code conventions which are ubiquitously used by programmer to outline their intentions.
Python's if __name__ == '__main__': suite encourages re-use and test driven development.
For example, the night before last I hacked together to run thousands of ssh jobs (with about 100 concurrently) and gather up all the results (output, error messages, exit values) ... and record the time take on each. It also handles timeouts (An ssh command can stall indefinitely on connection to a thrashing system --- it's connection timeouts and retry options don't apply after the socket connection is made, not matter if the authentication stalls). This only takes a few dozen lines of Python and it's really is easiest to create it as a class (defined above the __main__ suite) and do my command line parsing in a simple wrapper down inside __main__. That's sufficient to do the job at hand (I ran the script on 25,000 hosts the next day, in about two hours). It I can now use this code in other scripts as easily as:
from sshwrap import SSHJobMan
cmd = '/etc/init.d/foo restart'
targets = queryDB(some_criteria)
job = SSHJobMan(cmd, targets)
job.start()
while not job.done():
completed = job.poll()
# ...
# Deal with incremental disposition of of completed jobs
for each in sorted(job.results):
# ...
# Summarize results
... and so on.
So my script can be used for simple jobs ... and it can be imported as a module for more specialized work that couldn't be described on my wrapper's command line. (For example I could start up "consumer" subprocesses for handling other work on each host where the job was successful while spitting out service tickets or automated reboot requests for all hosts reporting timeouts or failures, etc).
For modules which have no standalone usage I can use the __main__ suite to contain unit-tests. Thus every module can contain its own tests ... which, in fact, can be integrated into the "doc strings" using the doctest module from the standard libraries. (Which, incidentally, means that properly formatted examples in the documentary comments can be kept in sync with the implementation ... since they are parts of the unit-test suite).
The main thing I like about Python is its very concise, readable syntax. Though using indentation as a block delimiter can seem strange at first, once you begin to code a lot in the language I find it begins to make sense. Though the core language is quite simple, its more advanced features, e.g. list comprehension, decorators and generators, are rather useful too.
In addition, the Python standard library is just fantastic; its documentation is very well written, and it contains a lot of very useful packages. I also find that there are plenty of good bindings for C libraries, such as PyGTK, Webkit and Qt, to name but a few.
One caveat is that Python, like most dynamic languages, is quite slow in comparison with compiled, statically-typed languages. However, you can easily extend it with C, allowing you to write code requiring better performance in C and the rest in Python.
It's a great language overall, and (for me at least) makes coding more productive and enjoyable.
What is the best way to build a parser in c# to parse my own language?
Ideally I'd like to provide a grammar, and get Abstract Syntax Trees as an output.
Many thanks,
Nestor
I've had good experience with ANTLR v3. By far the biggest benefit is that it lets you write LL(*) parsers with infinite lookahead - these can be quite suboptimal, but the grammar can be written in the most straightforward and natural way with no need to refactor to work around parser limitations, and parser performance is often not a big deal (I hope you aren't writing a C++ compiler), especially in learning projects.
It also provides pretty good means of constructing meaningful ASTs without need to write any code - for every grammar production, you indicate the "crucial" token or sub-production, and that becomes a tree node. Or you can write a tree production.
Have a look at the following ANTLR grammars (listed here in order of increasing complexity) to get a gist of how it looks and feels
JSON grammar - with tree productions
Lua grammar
C grammar
I've played wtih Irony. It looks simple and useful.
You could study the source code for the Mono C# compiler.
While it is still in early beta the Oslo Modeling language and MGrammar tools from Microsoft are showing some promise.
I would also take a look at SableCC. Its very easy to create the EBNF grammer. Here is a simple C# calculator example.
There's a short paper here on constructing an LL(1) parser here, of course you could use a generator too.
Lex and yacc are still my favorites. Obscure if you're just starting out, but extremely simple, fast, and easy once you've got the lingo down.
You can make it do whatever you want; generate C# code, build other grammars, emulate instructions, whatever.
It's not pretty, it's a text based format and LL1, so your syntax has to accomodate that.
On the plus side, it's everywhere. There are great O'reilly books about it, lots of sample code, lots of premade grammars, and lots of native language libraries.
I’m starting a project where I need to implement a light-weight interpreter.
The interpreter is used to execute simple scientific algorithms.
The programming language that this interpreter will use should be simple, since it is targeting non- software developers (for example, mathematicians.)
The interpreter should support basic programming languages features:
Real numbers, variables, multi-dimensional arrays
Binary (+, -, *, /, %) and Boolean (==, !=, <, >, <=, >=) operations
Loops (for, while), Conditional expressions (if)
Functions
MathWorks MatLab is a good example of where I’m heading, just much simpler.
The interpreter will be used as an environment to demonstrate algorithms; simple algorithms such as finding the average of a dataset/array, or slightly more complicated algorithms such as Gaussian elimination or RSA.
Best/Most practical resource I found on the subject is Ron Ayoub’s entry on Code Project (Parsing Algebraic Expressions Using the Interpreter Pattern) - a perfect example of a minified version of my problem.
The Purple Dragon Book seems to be too much, anything more practical?
The interpreter will be implemented as a .NET library, using C#. However, resources for any platform are welcome, since the design-architecture part of this problem is the most challenging.
Any practical resources?
(please avoid “this is not trivial” or “why re-invent the wheel” responses)
I would write it in ANTLR. Write the grammar, let ANTLR generate a C# parser. You can ANTLR ask for a parse tree, and possibly the interpreter can already operate on the parse tree. Perhaps you'll have to convert the parse tree to some more abstract internal representation (although ANTLR already allows to leave out irrelevant punctuation when generating the tree).
It might sound odd, but Game Scripting Mastery is a great resource for learning about parsing, compiling and interpreting code.
You should really check it out:
http://www.amazon.com/Scripting-Mastery-Premier-Press-Development/dp/1931841578
One way to do it is to examine the source code for an existing interpreter. I've written a javascript interpreter in the D programming language, you can download the source code from http://ftp.digitalmars.com/dmdscript.zip
Walter Bright, Digital Mars
I'd recommend leveraging the DLR to do this, as this is exactly what it is designed for.
Create Your Own Language ontop of the DLR
Lua was designed as an extensible interpreter for use by non-programmers. (The first users were Brazilian petroleum geologists although the user base has broadened considerably since then.) You can take Lua and easily add your scientific algorithms, visualizations, what have you. It's superbly well engineered and you can get on with the task at hand.
Of course, if what you really want is the fun of building your own, then the other advice is reasonable.
Have you considered using IronPython? It's easy to use from .NET and it seems to meet all your requirements. I understand that python is fairly popular for scientific programming, so it's possible your users will already be familiar with it.
The Silk library has just been published to GitHub. It seems to do most of what you are asking. It is very easy to use. Just register the functions you want to make available to the script, compile the script to bytecode and execute it.
The programming language that this interpreter will use should be simple, since it is targeting non- software developers.
I'm going to chime in on this part of your question. A simple language is not what you really want to hand to non-software developers. Stripped down languages require more effort by the programmer. What you really want id a well designed and well implemented Domain Specific Language (DSL).
In this sense I will second what Norman Ramsey recommends with Lua. It has an excellent reputation as a base for high quality DSLs. A well documented and useful DSL takes time and effort, but will save everyone time in the long run when domain experts can be brought up to speed quickly and require minimal support.
I am surprised no one has mentioned xtext yet. It is available as Eclipse plugin and IntelliJ plugin. It provides not just the parser like ANTLR but the whole pipeline (including parser, linker, typechecker, compiler) needed for a DSL. You can check it's source code on Github for understanding how, an interpreter/compiler works.