I have a C program with an embedded Perl interpreter. I want to be able to precompile some Perl code from within the program. How do I do that?
Rationale (if anyone is interested) is to be able to compile it once, store the parse tree, and execute many times (as long as the compiled code does not change).
Thanks!
Madhu
PS: I am using Perl-5.8, though it would be good to know if Perl-6.0 makes this easier in any way.
This is the default behavior when you embed the Perl interpreter in a C program. After you've run perl_parse() to parse the Perl program, you can use perl_run() and call_argv() over and over with the same parsed Perl program.
You can use perlcc to create executable or C sources.
To compile your C code, you would need to use perl's library (could be -lperl or -llibperl).
In reference to Perl 6, it's not complete. But 5.10.0 might have some bug fixes over 5.8.
Related
Is it possible to run a c macro function at compile time.
for example writing something in a file each time code is compiled.
Yes; No.
The macros do execute at compile time but there isn't much you can do directly with them other than mix text into the code.
Now, taking the software tools approach that unix pioneered (after all) you could conditionally generate output with #warning and then catch this with some script via a pipe.
Then that script could do stuff.
But, you probably wouldn't want to do that. Once you are running a script you could just have that script do whatever you want. Also, #error and #warning don't macro-expand the error or warning text, so using them for I/O is problematic.
This is obvious, I suppose, but how about using Ruby, Python, or the shell to script some macro processing?
Macros in C are strictly a text substitution tool. The output of the preprocessor is a preprocessed file.
So no, you can't do additional tasks like that from the preprocessor.
If you really want to perform certain tasks at compile time, that's what make is for.
Most of the examples online of C-to-Lua implementations show the C program messing around with Lua States and Compilers and even compiling both files in a special way to work properly.
But is there a way to call a C function from Lua without the C program knowing it will be used in a Lua program?
I mean something like loading a Lua library: to do that, I just call
module = require("/path/library")
module.doSomething()
from a standard Lua interpreter, while the examples of C-to-Lua I found online say not only you have to modify your C program to fit whit Lua, but you also need to compile them in a special way and things like that.
So, again, is it possible to call a C function from a standard Lua interpreter whitout the C module knowing it will be used in Lua?
I don't know if it can be of any help, but I'm using LuaJIT.
Use the FFI library that is integrated into LuaJIT.
So let's say I have a string containing some code in C, predictably read from a file that has other things in it besides normal C code. How would I turn this string into code usable by the program? Do I have to write an entire interpreter, or is there a library that already does this for me? The code in question may call subroutines that I declared in my actual C file, so one that only accounts for stock C commands may not work.
Whoo. With C this is actually pretty hard.
You've basically got a couple of options:
interpret the code
To do this, you'll hae to write an interpreter, and interpreting C is a fairly hard problem. There have been C interpreters available in the past, but I haven't read about one recently. In any case, unless you reallY really need this, writing your own interpreter is a big project.
Googling does show a couple of open-source (partial) C interpreters, like picoc
compile and dynamically load
If you can capture the code and wrap it so it makes a syntactically complete C source file, then you can compile it into a C dynamically loadable library: a DLL in Windows, or a .so in more variants of UNIX. Then you could load the result at runtime.
Now, what normally would lead someone to do this is a need to be able to express some complicated scripting functions. Have you considered the possibility of using a different language? Python, Scheme (guile) and Lua are easily available to add as a scripting language to a C application.
C has nothing of this nature. That's because C is compiled, and the compiler needs to do a lot of building of the code before the code starts running (hence receives a string as input) that it can't really change on the fly that easily. Compiled languages have a rigidity to them while interpreted languages have a flexibility.
You're thinking of Perl, Python PHP etc. and so called "fourth generation languages." I'm sure there's a technical term in c.s. for this flexibility, but C doesn't have it. You'll need to switch to one of these languages (and give up performance) if you have a task that requires this sort of string use much. Check out Perl's /e flag with regexes, for instance.
In C, you'll need to design your application so you don't need to do this. This is generally quite doable, as for its non-OO-ness and other deficiencies many huge, complex applications run on well-written C just fine.
Hi I wanted to know how to use MATLAB as an external solver from a C program. Specifically in my code I wish
to solve several linear systems of the form Ax=b.
I have heard that to go the other way namely Calling C functions in a MATLAB routine one uses MEX files.But I am not really sure how to use Mex files either.
Thank you
Actually, MEX files allow you to include C code in Matlab programs, for example if you want to use external C libraries in Matlab.
What you want to do is use the Matlab Engine:
http://www.mathworks.com/help/techdoc/matlab_external/f29148.html
As an alternative, you could use linear algebra libraries that are written purely in C, such as LAPACK and BLAS. ( www.netlib.org )
you can use the matlab engine as Lagerbaer points out. However sometimes it can be convenient just calling the matlab process commandline style. I use this often when I don't want to mess with mxArrays etc, or when the amount of matlab code that needs executing gets really large. PseudoCode:
WriteArrayInMFormat( "in.m", myInputNumbers );
LaunchProcess( "matlab", "-nodesktop -r \"myFunction( 'in.m' )\" -logfile out.m" );
ReadArrayInMFormat( "out.m", myResult );
For me this is especially useful when testing things out: instead of having to recompile the C/C++ program each time I change something, I just apply all changes in the myFunction.m file. At that point I don't even need the C program, instead everything can be tested in matlab.
Does anyone know of any tool which can convert shell script '.sh' into a C file '.c' ?
I doubt that any such tool exists. C and shell files are extremely different languages with completely different purposes, and there is no way to automatically convert one to the other.
you can try shc. Its not a compiler, but it does generate .c files during encoding/encrypting.
Otherwise, do it by hand. Learn to code in C and shell, then translate them yourself. that's the best way to do it.