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From: cushman@cpsin2.cps.msu.edu (Roderick J Cushman)
Newsgroups: comp.databases
Subject: Re: So does Clipper do it ?
Keywords: Clipper Index gauge, .NTX file, dbCreatIndex()
Message-ID: <1991May24.180404.18538@msuinfo.cl.msu.edu>
Date: 24 May 91 18:04:04 GMT
References: <1991May23.182713.5914@beach.csulb.edu> <29737@hydra.gatech.EDU> <1991May24.173628.15324@msuinfo.cl.msu.edu>
Sender: news@msuinfo.cl.msu.edu
Reply-To: cushman@cpsin2.cps.msu.edu (Roderick J Cushman)
Organization: Dept. of Computer Science, Michigan State University
Lines: 74
Originator: cushman@cpsin2.cps.msu.edu

In article <1991May24.173628.15324@msuinfo.cl.msu.edu> cushman@frith.cps.msu.edu (PUT YOUR NAME HERE) writes:
>   ... NULL posting; please accept my apology...  The following is what I 
>>      intended to post...

        Hi:

        (I apologize for the previous NULL posting)

                After perusing multiple articles discussing the usage of
        an index gauge (and reading the methods used), I thought I would
        attempt to shed some light (or more mud ???) upon the subject.

                Internal to Clipper version 5.0 (and I believe it is
        now documented in version 5.01) is a function called dbCreatIndex()
        (spelling ??).  I would have to look up the actual spelling of the
        function;  it can be found if you pre-process your code, then
        observe the .PPO file relevant to the INDEX ON <expr> to file.
        The parameters to the function are as follows:
 
        dbCreatIndex( cFileName, cFileExpr, bCreatExpr, lUniqflag)

                cFileName:   The name of the .NTX file to be created

                cFileExpr:   The expression to be placed in the index
                             (.NTX) file header.

                bCreatExpr:  a code block (similar to cFileExpr) which
                             is used to create the index tables.

                lUniqFlag:   a logical parameter which indicates to the
                             internal function whether the user wished
                             to INDEX ON <expr> to FILE UNIQUE
                                                        ^^^^^^


        If you examine the preprocessed code, the lUniqFlag parameter is
        an interesting if(...) conditional.  I am not sure why this was
        implemented in this manner, but a simple .T. or .F. value will
        suffice.

        You can pass to the .NTX file the expression (minus any display
        function calls), and pass to the code block the same expression,
        appended with any display function calls the user wishes.

        I tried to implement a BARCHART() routine, provided by either Rick
        Spence or Steven Straley & Assoc. (I cannot recall which book I 
        derived it from) in Summer '87.  Like the other messages I have
        read, using this feature in Summer '87 is a precarious position
        to uphold.  With the new versions (5.0*), seperating the code
        block from the file expression allows the programmer to cleanly
        perform video output of graphs, percentages, etc.

        Incidently, I have implemented the above code, deriving the params
        from a database (containing filenames, expressions, code blocks,
        unique flags, etc) and a revised function originated from the 
        people at Nantucket's tech support (theirs required a fixed position,
        color, etc.).  If anyone would like to see it, I could post a
        sample of it on the net (or email it individually).  

        I am a graduating student at this university (Michigan State U.)
        on June 8th.  I am not sure how long I will still be able to use
        this account after that.  I can be reached via the following office
 
        Rod Cushman
        W26 Holmes Hall
        Michigan State University
        East Lansing, MI, 48823

        if I cannot be contacted via the net...

        There is more information regarding indexxing, but, alas, I must
        be off to work...

Rod.