Actionscript parsing experiences: PyBison & PLY

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Last day I founded a python library (pybison) which runs the generated python parser at near the speed of C-based parsers, due to direct hooks into bison-generated C code.
Cool, unfortunately I couldn’t compiled it for Windows and so I made my test on Ubuntu only. What I did was just to export the already written lexer/grammar using bison2py (boundled with pybison) and run it.

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The run.py file accept these parameters:

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usage: run.py [options]
options:
-h, --help            show this help message and exit
-v, --verbose         Turn on verbose mode
-o OUTPUT_FILE, --output=OUTPUT_FILE
Don't print to stdout but to the output file
-i INPUT_FILE, --input=INPUT_FILE
Input file to be parsed
-x, --to-xml          Returns a human-readable xml representation of the
parse tree
-b, --bison-debug     Print the Bison/Flex debug

Cv Writing Service Waterford The second test I did was using PLY, an implementation of lex and yacc parsing tools for Python. Being implemented entirely in python it should be much more slower that pybison, but I didn’t find any difference with the pybison parser version. In fact PLY , like the traditional bison, creates tables starting from the grammar syntax.
Ok, Both of the implementations are slower that the pure C parser, but extremely faster that antlr!
(They took more or less 0.02 to 0.5 secs for parsing and generating the AST.)
Unlike pybison PLY is still mantained and offers more features and a better error handling.. even if the whole grammar has to be rewritten in python, and it can be compiled in Windows too.

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python run.py {filename}

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ActionScript Parsing, the YACC revenge :)

So first I need to wrote from scratch the grammar/lexer files using only the ECMAScript 4 specifications and much patience (the elastic grammar file help me a lot too).

http://www.hospitaldelsur.gov.co/?dance-your-dissertation-science Dance Your Dissertation Science The result was unbelievable: 0.02 seconds for that file!

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Problems In Writing Essays Now, the next step is to finish and test the parser and finally create a python library using pyrex, then a benchmark test again.

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An experience with antlr, java and python

http://www.otradny.org/?writing-reports-for-money Writing Reports For Money I was trying first to create the parser using GNU Flex and Bison in C, probably the best way for a very performancing parser.
Yeah, that’s right.. but looking at the antlr syntax I realized that’s easier and easier.
Moreover I start using this very useful eclipse plugin for antlr debugging which made my life easier!

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package org.sepy.core.parsers.as3;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import antlr.CommonAST;
import antlr.RecognitionException;
import antlr.TokenStreamException;
public class Application {
public static void main(String argv[])
{
if(argv.length > 0)
{
File file = new File(argv[0]);
if(file.exists())
{
FileInputStream is = null;
try {
is = new FileInputStream(file);
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
AS3Lexer L = new AS3Lexer(is);
AS3Parser P = new AS3Parser(L);
try {
P.compilationUnit();
} catch (RecognitionException e) {
// TODO Auto-generated catch block
System.out.println(" line=" + e.line + ", column="+ e.column);
System.out.println(e.getMessage());
e.printStackTrace(System.err);
} catch (TokenStreamException e) {
// TODO Auto-generated catch block
System.out.println(" line=" + L.getLine() + ", column="+ L.getColumn());
System.out.println(L.getGuessInfo());
System.out.println(e.getMessage());
e.printStackTrace(System.err);
}
CommonAST.setVerboseStringConversion(false, P.getTokenNames());
CommonAST ast = (CommonAST) P.getAST();
System.out.println("Tree:");
System.out.println(ast.toStringTree());
}
}
}
}

Writing 1 2 Page Essay Everything works fine also for python, but I realized that the python script were so much slower than the java one!

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import sys
import antlr
import AS3Parser
import AS3Lexer
L = AS3Lexer.Lexer(filename);
P = AS3Parser.Parser(L);
P.setFilename(filename)
try:
   P.compilationUnit();
   ast = P.getAST();
except:
   pass

So I run the python hotshot profiler to see which could be the bottleneck in the python script and I found most of the problems were due to unuseless antlr (the python module) method’s calls.
After making corrections to the antlr.py file the same script took exactly half of the time. Now 3 seconds. Wow 🙂
But not fast enough.
So I enabled for the antlr python script psyco module and this time the same script took Cheap Dissertation Writing Services Websites only 1.6 seconds.
Now the python script is fast enough, even if I’m sure I can make more optimizations in the antlr module…