In this question somebody asked about the C# equivalent for java ParseTree class in ANTLR4. That answer is clear for me, but I have a related, previous, question: which is the equivalent for parser.prog()?
It seems that the whole processing starts from this point, calling parser.prog(), and I must be doing some very wrong thing as I cannot find the method prog() in myGrammarParser class. I've searched the github source for its base class Parser, but no prog() Method here neither.
I did some guessing, just in case the method had a different name, but no luck.
I think I'm moving back to ANTLR3, as I found some working example for ANTLR3 targeting C#. It's a pity that it's so hard getting this to work.
Thanks in advance.
The prog() method was created because the grammar contains a rule prog. If the starting rule were named something else, e.g. compilationUnit, then you would call the compilationUnit() method to parse the input.
This particular aspect of ANTLR did not change between ANTLR 3 and ANTLR 4.
Related
The customer has million lines of code (VB.Net and C#), and wants us to develop a tool to estimate the quality of the code.
What the information the customer wants to know include:
1）how many lines of comments in one code file
2) how many functions implemented in one class
3) whether all possible exception has been wrapped by a try/catch block
4) how many attributes attached to one function
5) ... (the customer said that the tool we provide should be configured and extensible so that they can implement more ideas later)
We plan to write a VS.Net add-on, which can parse the code of the opening project in time. seems the interesting thing in here is that we need to parsing the code of C# and VB.Net.
Please kindly provide some tips about how to start this interesting task.
Thanks in advanced!
You ask a very broad question, but you should begin by studying existing parser's APIs.
Once you do that you're golden.
For example look at this SO question which provides some parsers for C#. Of course you could write your own but I don't find any reason to since the task isn't very easy.
So you get your AST and once you do that you have all the information you want.
Keep in mind that if you reference a type that isn't in the file you must have to get it from another one, and it could also be a type from .NET. So there is definitely more work to be done.
To go through your list:
1）how many lines of comments in one code file: You could find it through your C# parser of choice. They recognize comment aswell
2) how many functions implemented in one class: Likewise, should be very easy
3) whether all possible exception has been wrapped by a try/catch block: Likewise, just find exception throws (the parser is likely to have a special type for language keywords, so looking for throw should be easy).
4) how many attributes attached to one function: and... Likewise
5) ... (the customer said that the tool we provide should be configured and extensible so that they can implement more ideas later): Shouldn't differ from any other project. Just make sure you're using good design principles, keeping everything abstract, using interfaces wisely, make your work in layers, etc. etc...
You can use Roslyn. For C# you can also use NRefactory.
Have a look at Stylecop, you may be able to add rules get the information you want?
http://stylecop.codeplex.com/
I am asking this question, because I didn't find yet any posts that are C# related and there might be some build in methods for that I couldn't find. If there are, please tell me so and I can close this question.
Basically I have the common situation:
User types a function w.r.t. one or two variables into some TextBlock
I take this string analyse it
As a return I would like to have a delegate to a method that will take one or two inputs (the variables) and return the function value according to what the user typed in.
Now, I could probably think (and I would like to do this on my own, because I want to use my brain) of an algorithm of analysing the string step by step to actually find out, what has to be calculated first and in what way. E.g. First scan for parentheses, look for the expression within a group of parantheses and calculate that according to more general functions etc.
But in the end I would like to "create" a method of this analysis to be easily used as a normal delegate with a couple of arguments that will return the correct function value.
Are there any methods included in C# for that already, or would I have to go and program everything by myself?
As a remark: I don't want to use anybody else' library, only .NET libraries are acceptable for me.
Edit: After Matt pointed out expression trees, I found this thread which is a good example to my problem.
Edit2: The example pointed out does only include simple functions and will not be useful if I want to include more complex functions such as trigonometric ones or exponentials.
What you are describing is a parser. There are a number of different ways of implementing them, although generally speaking, for complex grammars, a "parser generator" is often used.
A parser generator will take a description of the grammar and convert it into code that will parse text that conforms to the grammar into some form of internal representation that can be manipulated by the program, e.g. a parse tree.
Since you indicate you want to avoid third-party libraries, I'll assume that the use of a parser generator is similarly excluded, which leaves you with implementing your own parser (which fortunately is quite an interesting exercise).
The Wikipedia page on Recursive descent parsers will be particularly useful. I suggest reading through it and perhaps adapting the example code therein to your particular use case. I have done this myself a number of times for different grammars with this as a starting point, so can attest to its usefulness.
The output from such a parser will be a "parse tree". And you then have a number of possibilities for how you convert this into an executable delegate. One option is to implement an Evaluate() method on your parse tree nodes, which will take a set of variables and return the result of evaluating the user's expression. As others have mentioned, your parse tree could leverage .NET's Expression trees, or you can go down the route of emitting IL directly (permitting you to produce a compiled .NET assembly from the user's expression for later use as required).
You might want to look at expression trees.
Check out NCalc for some examples of how to do this. You don't need to use the library, but reading the source is pretty educational.
I found a very helpful pdf explaining the parsing in C# 2.0. This link leads to a very good tutorial on parsers used in C# and also applies that later on to an arithmetic expression.
As this directly helps and answers to my question, I posted this as an answer, rather than as a comment or edit.
I am researching ways, tools and techniques to parse code files in order to support syntax highlighting and intellisence in an editor written in c#.
Does anyone have any ideas/patterns & practices/tools/techiques for that.
EDIT: A nice source of info for anyone interested:
Parsing beyond Context-free grammars
ISBN 978-3-642-14845-3
My favourite parser for C# is Irony: http://irony.codeplex.com/ - i have used it a couple of times with great success
Here is a wikipedia page listing many more: http://en.wikipedia.org/wiki/Compiler-compiler
There are two basic aproaches:
1) Parse the entire solution and everything it references so you understand all the types involved in the code
2) Parse locally and do your best to guess what types etc are.
The trouble with (2) is that you have to guess, and in some circumstances you just can't tell from a code snippet exactly what everything is. But if you're happy with the sort oif syntax highlighting shown on (e.g.) Stack Overflow, then this approach is easy and quite effective.
To do (1) then you need to do one of (in decreasing order of difficulty):
Parse all the source code. Not possible if you reference 3rd party assemblies.
Use reflection on the compiled code to garner type information you can use when parsing the source.
Use the host IDE's (if avaiable - so not applicable in your case!) code element interfaces to provide the information you need
You could take a look at how http://www.icsharpcode.net/ did it. They wrote a book doing just that, Dissecting a C# Application: Inside SharpDevelop, it even has a chapter called
Implement a parser to provide syntax
highlighting and auto-completion as
users type
first things first;
I am writing a little LUA-Ide in C#. The code execution is done by an Assembly named LuaInterface. The code-editing is done by a Scintilla-Port & the RAD / UI Interface is via the extensible IDesignSurfaceExt Visual Studio (one way code generation). File handling is provided by a little sql-lite-db used as a project-package-file.
So all in all i've got everything i need together...
The only problem unsolved is the parser / lexer for lua. I do not want to load & execute the code! I just want to parse the String containing the Lua code and get some information about it like function and global vars. I really don't want to write the parser completly myself... (I hate regex - I get the wrong all the time ^^)
Anybody got a link to a .net lua parser lying around?
Just to clarify - I only want to analyse the code at this point - I dont wnat to run it!
Thanks in advance!
Corelgott
Just for the record:
I went with a comibination of:
http://irony.codeplex.com/ - A Language implementation Kit that can be adapted to parse several languages. (Btw. this one got virtually no ducumentation what so ever... So code-comments no docs... but lots of fun...)
and a customized version of
http://luairony.codeplex.com/ - the Lua Syntax for irony (added some degree error tolerance)
But I gotta admin, both are pretty heavy stuff... and you kind of open up a box of new problems as well as lots of possibilities...
Cheers, Corelgott
This SO question's responses may be helpful.
Easiest way to parse a Lua datastructure in C# / .Net
Incomplete but:
http://luairony.codeplex.com/
This isn't quite what you're after, but maybe half of it can provide half the answer.
It converts Lua to C, by parsing the Lua to an AST. You could then extract the info you need from the AST. It's written in Lua, but you already know how to call that :)
Have look here: Lua recipes for LPeg
Maybe you can use one - otherwise I would look at using the extended BNF from the documentation.
I require the ability to preprocess a number of C# files as a prebuild step for a project, detect the start of methods, and insert generated code at the start of the method, before any existing code. I am, however, having a problem detecting the opening of a method. I initially tried a regular expression to match, but ended up with far too many false positives.
I would use reflection, but the MethodInfo class does not reference the point in the original source.
EDIT: What I am really trying to do here is to support pre-conditions on methods, that pre-condition code being determined by attributes on the method. My initial thought being that I could look for the beginning of the method, and then insert generated code for handling the pre-conditions.
Is there a better way to do this? I am open to creating a Visual Studio Addin if need be.
This is a .NET 2.0 project.
Cheers
PostSharp or Mono.Cecil will let you do this cleanly by altering the generated code without getting into writing a C# parser which is unlikely to be core business for you...
Havent done anything of consequence with PostSharp but would be guessing its more appropriate than Mono for implementing something like preconditions or AOP. Alternately you might be able to do something AOPy with a DI container like Ninject
But of course the applicability of this idea Depends - you didnt say much other than that you wanted to insert code at the start of methods...
EDIT: In light of your desire to do preconditions... Code Contracts in .net 4 is definitely in that direction.
What sort of a tool do you have? Whats wrong with having a single Mono.Cecil.dll DLL shipped? Either way something other than a parser is the tool for the job.
I am sure there is an easier way but this might be a good excuse to take MGrammer for a spin.