I need Improved Perlin Noise in my Lua code.
Are there any decent open-source Lua C modules available?
Or is there any nice C library that I can write a wrapper for (perhaps with other noise functions)?
I know that it is not hard to write one myself (reference code in Java is trivial to port), but I do not want to reinvent the wheel here.
Ah, well, I'll have to roll my own then: http://github.com/agladysh/lua-noise/
Related
I am writing code for rrt(rapidly exploring random trees) which is a sampling based motion planning algorithm.I wrote the code in MATLAB but now i am writing it in c++.
I want to know how can we plot the robot path in real time with all the obstacles.
What I want is this: I want to see my robot traversing the space.So basically it's about the graphics.I am trying to use sfml but I am having problems with it.Some people suggested using opencv or opengl but I think they are not easy to use.I am looking for a simple to use library.
If opencv or opengl is the answer then please tell me what specifically i need to use in these libraries.I am working on linux(ubuntu 11.10)
You might want too look into using the internal matlab compiler for generating a standalone application directly from your M-code. That way you don't have to rewrite everything form scratch.
I have used the following link a couple of times just to refresh my memory
http://technologyinterface.nmsu.edu/5_1/5_1f/5_1f.html
Eg if you have made an M function with the following content(Example from link):
function y=PolyValue(poly,x)
poly=[1 2 -1 4 -5];
x=[5, 6];
y=polyval(poly, x)
you could use the command
mcc -m PolyValue
to compile the program.
This command would then give you the files necessary for implementation in a larger c++ program.
It should even support Gui elements and graphs.
Something like http://www.ros.org/news/2011/01/open-motion-planning-library-ompl-released.html
may be what you are looking for.
I've worked in both OpenCV for some image recognition projects and OpenGL for rendering displays and whether you go with a library like above or render it yourself is really up to how complex the display needs to be. Ask yourself some questions about how many different obstacle scenarios you are looking at. Are there a large multitude of possible shapes for the obstacles and the robot? Is the problem deterministic (in terms of both the robot's movement and the environment)?
In terms of OpenGL and OpenCV being not easy to use for those new to them, this is very much the case, but choosing to work in C++ makes the problem more difficult for beginners. As another user has mentioned, wrapping your Matlab code instead of throwing it away may be a viable option. Even running the matlab engine in the background to run your scripts through C++ may be viable, if speed is not a critical factor. See http://au.mathworks.com/help/matlab/matlab_external/introducing-matlab-engine.html for more information.
I've just finished a library in Objective-C that I compiled as a Static Library for distribution.
I'd wanted to know what chances to get this decompiled are out there.
Do you know any software that can do this?
If so, how could I protect me better?
EDIT: My static lib is made for iPhone / ARM
I created an algorithm that depending on the some parameters of the app, it can run as demo or as full code. You init the object with X variables and unlock the full version. I was wondering if they'll be able to see this algorithm so they can create a key generator.
If it executes, it can be decompiled. Objective-C is particularly easy to decompile into readable code thanks to its dynamic features. If you want to make things a little bit harder, you could write most of your code in plain C and strip the executable — which of course has the tradeoff of making your application design harder to manage. But be honest with yourself: If somebody wants to crack your code, you are not going to be able to stop them. Crackers have practically unlimited amounts of time and enthusiasm and will actually be excited by any novel efforts you put in to stop them. Nobody has yet made uncrackable software, and the biggest corporations in the world have tried. You're not going to do better than them, especially if you need to ask about it on Stack Overflow.
Take the time that you would have put into thwarting decompilation and use it to make your product better — that will have a much better ROI.
It's not clear what you are trying to protect yourself from. Yes, it can be reverse engineered. The simplest tool is otool, part of the standard developer distribution:
otool -tV <library>
From that they run up to things like IDA Pro, which has iPhone support and is very nice for this kind of work. In between, I'm really surprised that I haven't seen a rework of otx for iPhone/ARM yet. I wouldn't be surprised to see one show up eventually. And of course there's gdb if you're trying to work out how things flow and what the data is at various points.
If you have more details about what you're trying to protect yourself from, there may be some targeted answers. Beyond that, read Chuck's comments.
ChanceGetsDecompiled = ExpectedGainFromBeingDecompiled / PopularityOfLibrary
Well if you REALLY want to know I would try decompiling it your self. You don't say if this is for PPC, Intel, or ARM which makes a difference. Here is a decompiler for Intel
i386 Decompiler
I don't know what you could do (I don't think there is much) to limit this. Code can always be reverse engineered. Be happy that your not using java or .net. Their decompilation is so nice.
I'm thinking about writing my own little language.
I found a few options, but feel free to suggest more.
JVM
Parrot
OSA
A lot of languages are using the JVM, but unless you write a Java-ish language, all the power the stdlib gives you is going to feel ugly; It's not very good at dynamic stuff either.
Parrot seems a good VM for developing languages, but it has a little abandoned/unfinished/hobby project smell to it.
OSA is what powers Applescript, not a particularly well known VM, but I use Mac, and it offers good system integration.
CLR+Mac doesn't seem a good combination...
My language is going to be an object orientated functional concurrent dataflow language with strong typing and a mix of Python and Lisp syntax.
Sounds good, eh?
[edit]
I accepted Python for now, but I'd like to hear more about OSA and Parrot.
One approach I've played with is to use the Python ast module to build an abstract syntax tree representing the code to run. The Python compile function can compile an AST into Python bytecode, which exec can then run. This is a bit higher level than directly generating bytecode, but you will have to deal with some quirks of the Python language (for example, the fundamental difference between statements and expressions).
In doing this I've also written a "deparse" module that attempts to convert an AST back to equivalent Python source code, just for debugging. You can find code in the psil repository if you're interested.
Have a look at LLVM. It's not a pure VM as such, more a framework with it's own IR that allows you to build high level VMs. Has nice stuff like static code analysis and JIT support
Lua has a small, well-written and fast VM
Python VM - you can really attach a new language to it if you want. Or write (use?) something like tinypy which is a small and simple implementation of the Python VM.
Both options above have access to useful standard libraries that will save you work, and are coded in relatively clean and modular C, so they shouldn't be hard to connect to.
That said, I disagree that Parrot is abandoned/hobby. It's quite mature, and has some very strong developers working on it. Furthermore, it's specifically a VM designed to be targeted by multiple dynamic languages. Thus, is was designed with flexibility in mind.
Have you considered Pypy? From what I've read, in addition to being a Python JIT Compiler, it also has the capability to handle other languages. For example there is a tutorial which explains how to create a Brainfuck JIT compiler using Pypy.
What are the programming features that are missing in C++ and Java ?
For eg. You can't do recursive programming in QBasic ? You can't dynamically allocate memory in QBasic.
What would be the good to have features in C++, Java.
I think Lisp Programmers will be able to add a few.
I miss lambda expressions.
This answer deals only with C++
Things I miss from the syntax, or the standard library:
RegExp as part of the standard library
Threads as part of the standard library
Pointer to member methods (not objects!)
Properties would be nice (I have seen codes that emulate this via C++ preprocessor... note an nice looking code).
Some lower level networking API (sockets!), and higher level API (give me this file from this ftp, submit "this" to this site via POST).
This is the list of things I would like to see, but I assume other people will disagree with me.
Memory garbage collector is nice.
A n interface for a GUI toolkit - let MSVC map it to win32, and on Linux... (good question!)
A stable ABI. In C it's a standard - but on C++ we are still missing a few decades. I want also stable ABI between compilers - I want to compile one library in MinGW, the other with CL and all should work.
This is the list of things I want to see, but I know they will not get away:
Compatibility with C. Really, it's a myth right now. using namespace std killed it.
Include, headers. Most of the information is already available in the DLL/so/a/"library", do we really need to keep this bad decision from 30 years ago? If needed the compilers should keep information in the binaries.
The need for Makefiles - the compiler should be smart enough to know what to do with this code, from the code itself. Pascal is doing it quite good. I think also D.
(I might be wrong, please correct me) The official standard openly and freely available for viewing. Why should I pay for the official papers? Do I need to do it for HTTP? UTF8? Unicode?
I think this is a very subjective question. From a theoretical point of view there's nothing "missing" in Java because you can do everything you want to from the perspective of the outcome as an application.
As with QBasic - recursion may not be possible but that doesn't prevent you from changing your recursive algorithm to an iterative algorithm. Programming language theory tells us that you can do this with every recursive problem. So there's also nothing missing here.
I think what you mean are features that are "nice to have" - and here everyone has to decide for himself. I'd even say there are features in the language which would have been "nice not to have" such as static imports - but again this is my subjective opinion...
If I were looking to create my own language are there any tools that would help me along? I have heard of yacc but I'm wondering how I would implement features that I want in the language.
Closely related questions (all taken by searching on [compiler] on stackoverflow):
Learning Resources on Parsers, Interpreters, and Compilers
Learning to write a compiler
Constructing a simple interpreter
...
And similar topics (from the same search):
Bootstrapping a language
How much of the compiler should we know?
Writing a compiler in its own language
...
Edit: I know the stackoverflow related question search isn't what we'd like it to be, but
did we really need the nth iteration of this topic? Meh!
The first tool I would recommend is the Dragon Book. That is the reference for building compilers. Designing a language is no easy task, implementing it is even more difficult. The dragon book helps there. The book even reference to the standard unix tools lex and yacc. The gnu equivalent tools are called flex and bison. They both generate lexer and parser. There exist also more modern tools for generating lexer and parser, e.g. for java there are ANTLR (I also remember javacc and CUP, but I used myself only ANTLR). The fact that ANTLR combines parser and lexer and that eclipse plugin is availabe make it very comfortable to use. But to compare them, the type of parser you need, and know for what you need them, you should read the Dragon book. There are also other things you have to consider, like runtime environment, programming paradigm, ....
If you have already certain design ideas and need help for a certain step or detail the anwsers could be more helpful.
ANTLR is a very nice parser generator written in Java. There's a terrific book available, too.
I like Flex (Fast Lex) [Lexical scanner]
and Bison (A Hairy Yacc) [Yet another compiler compiler]
Both are free and available on all *NIX installations. For Windows just install cygwin.
But I old school.
By using these tools you can also find the lex rules and yacc gramers for a lot of popular languages on the internet. Thus providing you with a quick way to get up and running and then you can customize the grammers as you go.
Example: Arithmetic expression handling [order of precedence etc is a done to death problem] you can quickly get the grammer for this from the web.
An alternative to think about is to write a front-end extension to GCC.
Non Trivial but if you want a compiled language it saves a lot of work in the code generation section (you will still need to know love and understand flex/bison).
I never finished the complete language, I had used rply and llvmlite implements a simple foxbase language, in https://github.com/acekingke/foxbase_compiler
so if you want use python, rply or llvmlite is helpful.
if you want use golang, goyacc maybe useful. But you should write a lexical analyzer by hard coding by hand. Or you can use https://github.com/acekingke/lexergo to simplify it.