Re: Delimeters to split strings - C# Discussion Boards

5-Aug-09 18:19

Hello, I just want to know if its possible to include the delimiter in the string output??

For example:

char[] delim = new char[] {';', ' '};

and the output:

for(int
x=0;
x<5;
x++)

Is there a way without using regex class?

dan!sh 5-Aug-09 18:27

dan!sh

5-Aug-09 18:27

See String.Split method.

It's not necessary to be so stupid, either, but people manage it. - Christian Graus, 2009 AD

gamer11276-Aug-09 0:11

6-Aug-09 0:11

I think you didn't understand what i mean..What i really want to say is if for example i have a semi-colon which is a delimiter, is it possible to still include the semicolon to the splitted string?

For example:

string str = "for(int x=0; x<5; x++) Console.WriteLine("Hello");

in the above example, i want to split the string using the delimiter semi-colon, but at the same time i want it to be included in the splitted string.

For example, instead of this output:

for(int
x=0
x<5
c++)

I want this kind of output:

for(int
x=0;
x<5;
x++)

If you'll notice the semicolon, which is a delimiter is also included in my desired output...Is this possible?

Luc Pattyn5-Aug-09 23:50

5-Aug-09 23:50

Good luck with for ( int x = 0 ; x < 5 ; x++ )

Smile | :)

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gamer11276-Aug-09 0:47

6-Aug-09 0:47

Is there a way on how to ignore or delete the whitespace? I presume that using Trim() method wouldn't do the work.

Luc Pattyn6-Aug-09 0:53

6-Aug-09 0:53

The correct way to deal with all the problems you are going to encounter is to write a real lexer and parser.

You can choose not to, and implement some shortcuts; chances are someone will come up with a case you can't handle. Here is one example:

for (int i = 0; i < "this is not a for(; ; ) loop".Length; i++) {...}

proving you need to understand string literals to recognize a for statement.

Smile | :)

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gamer11276-Aug-09 1:07

6-Aug-09 1:07

Luc Pattyn wrote:
chances are someone will come up with a case you can't handle.

You're right about that. We'll be presenting our program next week and defend it like our real thesis. this is only a project that will apply data structures. And when i read about parsing there many ways on how to parse a statement. The one that I think will do our program done is the bottom - up parsing which uses a stack and a parse tree. Now the problem is i don't know where to get the pattern that i'll use to accomplish that. I think the best way is to somehow find a way on how to do that and state to our presentation the scope and limitations of our program.

And also since this is only a simple for loop parser, We can only have a one-line statement, meaning we don't have to include the two curly braces for a block statement.

Luc Pattyn6-Aug-09 1:14

6-Aug-09 1:14

gamer1127 wrote:
Is there a way without using regex class?

Of course there is. Regex is a tool, a non-essential tool. Anything you can do with a Regex, you can do without Regex too. It will take more code, it may or may not be more readable, and chances are it will be faster without Regex. See this test[^].

Smile | :)

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gamer11276-Aug-09 1:31

6-Aug-09 1:31

Your right...hehehehe...Now I'm changing the codes on how to verify the entered string using data structures discussed by our professor (stack and tree). Since there is a Stack Collection in C# I think that would make the work a bit easier. Before I changed all the code(That was only yesterday) I was eager to use the Regex class since it has all that i need. But when I can't find a way on how to verify the entered string using Regex I started to look at the harder way which has a long code.

My only problem now is how to verify the entered string..I'm thinking of the way the infix to postfix works using stack. I think that is similar with what i'll be doing to do the job.

Ah..By the way...Can i use the regex class on splitting the strings only? Then apply the stack and parse tree in verifying the string?

Luc Pattyn6-Aug-09 1:42

6-Aug-09 1:42

gamer1127 wrote:
Can i use the regex class on splitting the strings only?

Not really as my "not a for loop".Length example indicated.

Furthermore, most programming languages can be parsed by an "LALR" parser, meaning you have to backtrack only one token at most, hence you don't need to have all the input at once, which is fine for huge source files (on which a Regex would probably be very slow).

Smile | :)

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gamer11276-Aug-09 4:15

6-Aug-09 4:15

Ok then...Can you suggest any good reading materials about parsing that can be found on the web? I already read some in wikipedia but i feel that the explanations there is somewhat incomplete or very hard to understand. I just need to know the basics.

Also should i use the grammar rules(the ones with the terms 'non-terminals' and 'terminals') as my pattern? Or should i use other ways to meet my own criteria in parsing? Right now i'm trying to use the Stack Collection to check the syntax then pass it to a new array, just like how converting from infix to postfix works. What i need are some rules to really come up with that kind of process.

Luc Pattyn6-Aug-09 4:32

6-Aug-09 4:32

gamer1127 wrote:
Can you suggest any good reading materials about parsing that can be found on the web?

Not really, I learned what I wanted to know about the subject before they invented the internet. Laugh | :laugh:

The "Dragon Book" by Aho, Sethi and Ulmann is pretty good. Its real title is "Compilers: Principles, Techniques and Tools" or so.

You can go two ways:
- use a yacc-like program, that reads a BNF description and generates lexer/parser code
- create your own special-purpose lexer/parser, where the methods are probably based on the BNF production rules.

The hardest thing in a parser is parsing expressions; in C-like languages expressions can be almost anything. Now if all you need is something that can find delimiters in a correct and practical code block with only simple expressions, you can skip a lot of stuff. But IMO you do need to handle comments, string literals, and escape characters.

I doubt you will come up with a real good general-purpose C/C++/Java/C# parser in a matter of days...

Smile | :)

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gamer11276-Aug-09 5:15

6-Aug-09 5:15

Thank You Very Much for your inputs...Now I can continue creating my program.. Big Grin | :-D