[futurebasic] Re: Parsing

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From: wave@... (M Goodes)
Date: Sat, 29 Nov 1997 09:59:21 -0500
>I need my program to parse some fairly sizable text based files.  The file
>specification is quite loose, however, so I can't know exactly where each
>element of the file will be.  What I'm looking for is a fast way to locate,
>for example, the first character in the handle that is NOT a white space
>(CHR's 9 through 13) or the first character that IS the start of a
>subsection: ({[< and such.  I'm using some FN MUNGER code that was posted
>here a while back for most of my parsing, but I haven't found a way to do
>this with that yet.

Here's the basic idea of MUNGER:

 'h&=your text handle
 search$="("
 searchChar&=@search$+1        '  allow for length byte
 startOffset&=0
 openBracket&=FN MUNGER(h&,startOffset&,searchChar&,LEN(search$),0,0)

This returns the offset of the character in your text file, if found,
otherwise returns a negative number.
I'm not sure what the last two 0's are for--something to do with replacing
text, I think.

The limitation of MUNGER seems to be that you can only look for one search
string at a time.  So Tedd's solution might be quicker anyways, if you look
for more than one character at a time:
     LOCAL FN readByte                                 'read 1 byte
         DIM a, 2 a$
         a = PEEK ( [gTextH&] + gOffSet&)
         a$=chr$(a)
        select a$
        case "(", etc
        end select
         INC (gOffSet&)
     END FN = a

>
>While I'm at it, if anyone knows a way to search for a string that is not
>within a subsection (a pair of the above characters: {}, (), etc.) I'd
>appreciate hearing that, as well.  My current solution is to search for the
>string, and then search for the start and end of the subsections leading up
>to the string and making sure that the last subsection ends before the
>string begins.  It works, but it seems to me like there should be a faster
>method.

I assume you're looking for mathematical formulas.  Perhaps you could try
searching for the brackets first, and take action based on whether a
bracket has been opened yet.  In the SELECT part of the above code, you
could set flags like this:
        select a$
        case "{"
                openLarge=_true
        case "["
                openBracket=_true
        case "("
                openParenthesis=_true
        case "}"
                open large=_false
        etc.
        case else
                ...take action based on what is true at this point...

Hope this helps.

>Thanks in advance.
>
>-- Brian Victor
>
>
>--
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