[antlr-interest] Customizing token separators without recompiling

[J. Stephen Riley Silber]

Oh, I'm saying you wouldn't want to use a grammar at all.  The problem you've described is lexical, not grammatical.  If you simply want to break apart a line of text based on an arbitrary delimiter, it would be much easier to write a program in Perl, Python, Java, etc. that split the text based on a configuration setting.

If further parsing needs to happen on the newly-split fields, then you can attack that problem piecemeal on an individual basis.

Make sense?

--- On Sun, 6/7/09, Dukie Banderjee <dukie_banderjee at hotmail.com> wrote:

From: Dukie Banderjee <dukie_banderjee at hotmail.com>
Subject: RE: [antlr-interest] Customizing token separators without recompiling
To: jsrs701 at yahoo.com, antlr-interest at antlr.org
Date: Sunday, June 7, 2009, 2:30 PM




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Hi,

Sorry, I'm not following you. How would that work? E.g. A new customer comes along, they have their format that uses '_' (or whatever), and how do I get the lexer/parser to recognize their file format without re-generating/re-compiling the lexer/parser? What would Perl operate on? The grammar? Wouldn't that require re-generating/re-compiling the lexer?

Rob

Date: Sun, 7 Jun 2009 12:48:50 -0700
From: jsrs701 at yahoo.com
Subject: Re: [antlr-interest] Customizing token separators without recompiling
To: antlr-interest at antlr.org; dukie_banderjee at hotmail.com

Howdy,

I'm guessing there's more to the problem than just supporting arbitrary field separation tokens, because if that's all there is, just use something like perl and store the separator(s) in a config file...?

--S

--- On Sun, 6/7/09, Dukie Banderjee <dukie_banderjee at hotmail.com> wrote:

From: Dukie Banderjee <dukie_banderjee at hotmail.com>
Subject: [antlr-interest] Customizing token separators without recompiling
To: antlr-interest at antlr.org
Date: Sunday, June 7, 2009, 8:25 AM




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Hi everyone,

I'm new to the list and new to ANTLR. I have a specific problem I need to solve and I hope ANTLR can help.

Our client has several end-customers who all have slightly different document formats used for data interchange.

All the documents are basically 'standard' EDI documents, meaning they have the same basic syntax. However, some customers will use a '+' to separate values, some will use '*', others will use '~', etc. (I'm reminded of the old saying, "The great thing about standards is that there are so many to choose from!")

So, basically, the following inputs are all basically the same, except for the character used to separate tokens:
FST*4290*D*W*20070607
FST+4290+D+W+20070607
FST~4290~D~W~20070607

The thing is, we don't know ahead of time which separator characters might be used in the future, and we need to be able to tweak each end-customer's file format without re-compiling the
 lexer/parser. For example, a year from now there might be a customer who decides to use '_' or '$' or whatever, and we need to provide our client with a simple way (e.g. a per-customer configuration file) to customize the lexer/parser for such situations, without re-generating/re-compiling.

So, is this possible with ANTLR? How would I do this? Would it require a custom Lexer subclass with constructor parameters (e.g. new CustomLexer('_')) or something? How would this mesh with the generated lexer code from ANTLR?

I'm quite new to tools such as ANTLR (and parsers in general), so any help would be much appreciated. I really don't know where to start with this problem. For a hand-coded parser it's fairly simple, but I don't know enough about the workings of ANTLR to see where I would need to tweak it.

Thanks,

Rob

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