friends, I have a piece of code which can perform simple add, subtraction, multiplication, division, and formula with brackets.
Is there some kind of conversion tool for translating code from C to Smalltalk?
Or any other relatively easy way to achieve this?
Thanks in advance.
This should be trivial to write with PetitParser
There is an implementation of SWIG for Smalltalk. (SWIG is a software development tool that connects programs written in C and C++ with a variety of high-level programming languages).
Related
Any suggestion on how to use Lindenmeyer System approach (L-System) to make the GNU parser faster through parallelism. I also need to compare the normal execution time and execution time when the L-system is implemented for the C language. Any suggestion will be helpful.
Your question is too broad for this format. Note that you can write a very efficient parser for the C language without the L-System, the TinyCC compiler is a good example of a hand written C parser written int the C language that is very efficient. Check it out at http://tinycc.org
I've seen several implementations of recursive descent c interpreters which all seem
to do a pretty good job - yet they all only implement a small portion of the C language -
for example they don't support structs or typedefs etc -
Does anyone know of any code that supports a large portion of the C language.
I know adding more functionality would be pretty trivial - but I'm a bit strapped
for time.
Picoc supports more that most of the Tiny/Small C interpreters. You might give it a look. And it does support structures.
If you just want to use it, this one looks awfully good for the job. There was a Dr. Dobb's article on it a while back ... there it is
I am designing a compiler in C. I want to know which technique I should use, top-down or bottom up? I have only implemented operator precedence using bottom up. I have applied the following
rules:
E:=E+E
E:=E-E
E:=E/E
E:=E*E
E:=E^E
I want to know that am I going the right away?
If I want to include if-else, loops, arrays, functions, do I need to implement parsing?
If yes, how do I implement it? Any one can
I have only implemented token collection and operator precedence. What is the next steps?
Lex & Yacc is your answer. Or Flex and Bison which are branched version of original tools.
They are free, they are the real standard for writing lexers and parsers in C and used all around everywhere.
In addition O'Reilly has released a small pearl of 300 pages: Flex & Bison. I bought it and it really explains you how to write a good parser for a programming language and handle all the subtle things (error recovery, conflicts, scopes and so on). It will answer also your questions about how you are parsing expressions: your approach is right with a top-down parser but you'll discover that is not enough to handle operator precedences.
Of course, for hobby, you could write your own lexer and parser but it would be just an academic effort that is nice to understand how FSM and parser work but with no so much fun :)
If you are, instead, interested in programming language design or complex implementations I suggest this book: Programming Language Pragmatics that is not so famous because of the Dragon Book but it really explains why and how various characteristics can and should be implemented in a compiler. The Dragon Book is a bible too, and it will cover at a real low level how to write a parser.. but it would be sort of boring, I warn you..
The best way to implement a good parser in C is using flex & yacc
Your question is quite vague and hard to answer without a more specific, detailed question. The "Dragon book" is an excellent reference though for someone seeking to implement a compiler from scratch, or as others have pointed out Lex and Yacc.
If you intend to implement the parser by hand, you will want to do a recursive descent parser. The code directly reflects the grammar, so it's fairly easy to figure out and understand. It places some restrictions on your grammar (you can't have any left-recursive nonterminals), but you can work around those problems.
However, it depends on the complexity of the grammar; hand-hacking a parser for anything much more complicated than basic arithmetic expressions gets very tedious very quickly. If you're trying to implement anything that looks like a real programming language, use a parser generator like yacc or bison.
I am looking for ANSI C HAT-trie implementation released under some free license. I have not found one. Can you point me to some standalone implementation or a program that uses
HAT-tries to get at least slight idea how to implement it the roght way, please?
The original paper on HAT-trie can be found here:
http://crpit.com/confpapers/CRPITV62Askitis.pdf
PS: In case faster cache-conscious data structured well-suited for strings evolved since
the time the above paper was written, please point me to the papers or example source codes rather.
Someone is implementing it in C++ over on github
https://github.com/chris-vaszauskas/hat-trie
If you need a plain C implementation, this would be a good base to start from.
Java is also fairly readable for a C programmer
http://www.stochasticgeometry.ie/2008/05/06/implementing-hat-tries-in-java/
Please see the HAT-trie implementation site at code.google.com/p/hat-trie for implementation notes and source code.
I have a requirement for porting some existing C code to a IEC 61131-3 compliant PLC.
I have some options of splitting the code into discrete function blocks and weaving those blocks into a standard solution (Ladder, FB, Structured Text etc). But this would require carving up the C code in order to build each function block.
When looking at the IEC spec I realsied that the IEC Instruction List form could be a target language for a compiler. The wikepedia article lists two development tools:
CoDeSys
Beremiz
But these seem to be targeted compiling IEC languages to C, not C to IEC.
Another possible solution is to push the C code through a C to Pascal translator and use that as a starting point for a Structured Text solution.
If not any of these I will go down the route of splitting the code up into function blocks.
Edit
As prompted by mlieson's reply I should have mentioned that the C code is an existing real-time control system. So the programs algorithms should already suit a PLC environment.
Maybe this answer comes too late but it is possible to call C code from CoDeSys thanks to an external library.
You can find documentation on the CoDeSys forum at http://forum-en.3s-software.com/viewtopic.php?t=620
That would give you to use your C code into the PLC with minor modifcations. You'll just have to define the functions or function blocks interfaces.
My guess is that a C to Pascal translator will not get you near enough for being worth the trouble. Structured text looks a lot like Pascal, but there are differences that you will need to fix everywhere.
Not a bug issue, but don't forget that PLCs runtime enviroment is a bit different. A C applications starts at main() and ends when main() returns. A PLC calls it main() over and over again, 100:s of times per second and it never ends.
Usally lengthy calculations and I/O needs to be coded in diffent fashion than a C appliation would use.
Unless your C source is many many thousands lines of code - Rewrite it.
It is impossible. To be short: the IL language is a 4GL (i.e. limited to
the domain, as well as other IEC 61131-3 languages -- ST, FBD, LD, SFC).
The C language is a 3GL.
To understand the problem, try to answer the question, which way to
express in IL manipulations with a pointer? for example, to express call a
function by a pointer. What about interrupts? Low level access to the
peripherial devices?
(really, there are more problems)
BTW, there is the Reflex language, aka "C with processes". Reflex is a 4GL for the
control domain with C-like syntax. But the known translators produce
C-code and Python-code.
If the amount of code to convert is a few thousand lines, recoding by hand is probably your best bet.
If you have lots of code to convert, then an automated tool might be very effective.
Using the DMS Software Reengineering Toolkit we've built translators to map mechanical motion diagrams into RLL (PLC) code. DMS also has full C parser/analyzers/front ends. The pieces are there to build a C to RLL code.
This isn't an easy task. It likely takes 6-12 man-months to configure DMS to something resembling what you want. If that's less than what it takes to do by hand, then its the right way to do it.
There are a few IEC development environments and target hardware that can use C blocks... I would also take a look at the reasons why it HAS to be an IEC-61131 complaint target. I have written extensively on compliance and why it doesn't mean squat.
SOFTplc corp can help I'm sure with user defined loadable modules... and they can be in C..
Schneider also supports C function blocks...
Labview too!! not sure why IEC is important that's all!! the compiler if existed would create bad code for sure:)
Your best bet is to split your C code into smaller parts which can be recoded as PLC functional blocks and use C to PASCAL convertor for each block which you will rewrite in structured text. Prepare to do a lot of manual work since automated conversion will probably disappoint you.
Also take a look at this page: http://www.control.com/thread/1026228786
Every time I've done this, I just parsed and converted it by hand from C directly to ST. I only ran into a few functions that required complete rewrites, although there was very little that dealt with pointers, which is something that ST generally chokes on, unfortunately.
Using the existing C code as blocks that are called by the PLC program would have the added advantage that the C blocks could run at the same periodicity that they did before, and their function is likely already well documented and tested. This would minimize any effect on changes from the existing control system. This is an architecture for controls with software PLCs that I have seen used before.