Re: Lengthy discussion about datafile.c...

[Daniel J S. <dan...@ie...>]

Ethan Merritt wrote:

>On Saturday 14 August 2004 03:50 pm, you wrote:
>  
>
>>OK, let me back up here.  I think I see now the more important issue
>>here is that the data to be plotted, the imigration.dat file for
>>example, won't work because it has more columns than allowed by max_cols
>>passed into the df_readline routine.
>>    
>>
>
>No, that's completely wrong.  The data is being plotted 1 column at
>a time.  Sure there are lots of columns in the data file, but there's 
>nothing special about that.
>

OK, got it.

>Hint:  In the current code every requested column is returned
>twice, once as a number and once as a string.  The caller can 
>choose whether it wants the string value or the numeric value.
>I don't know how this fits in with your binary data files, but I
>assure you it is fully generic.  The histogram code doesn't use
>this anyhow; histogramming is not about strings, it's about
>columns of numbers.   You are, I am guessing, thinking about
>my *other* new plotting mode - 'with labels'.
>

Inside df_readline() is the if statement:

        if (use_spec[output].expected_type >= CT_XTICLABEL) {

and inside of that case is an instruction:

            if (df_current_plot) xpos += df_current_plot->histogram->start;

and inside of graphics.h is the definition of histogram for curve_points:

    struct histogram_style *histogram;    /* Only used if plot_style == 
HISTOGRAM */

If I follow, only the histogram plot style, then, can make use of that 
particular block of code inside df_readline().  That, or one needs to 
realize that the histogram->start can be used in a generic fashion.

I guess it isn't that big of a deal, but it just seems like the 
use_spec[] portion of df_readline() is growing very large and doing 
lot's of specific stuff.

>>Does this get around some problems?  Am I understanding the big issue
>>now, that there are more columns now than max_cols?
>>    
>>
>
>No. Nothing at all like that.  I want to get rid of max_cols not because
>I want lots of columns, but just because it is not used for anything that
>really has to do with columns.  It is only used to try to deduce back to
>what the plot type is - which I think is nuts. If you need to know the plot
>type then just pass the plot type.
>

Oh, well yeah guessing the structure from the max cols is kind of silly.

>>Well, here is the thing.  There is a certain element of this that can't
>>be disentangled (if that's a word).  A lot of the parameters for reading
>>from a file are set up by df_open() because it is there that the
>>keywords from the command line are processed.  So, at the point of
>>df_open() it isn't known yet whethere the file is ascii or binary.  That
>>could be fixed by first, at the start of df_open, checking all the
>>keywords to see if one is "binary", but that's not graceful.
>>    
>>
>
>Hunh?  Now I'm the one who is confused.  I really have not been
>looking at that part of your patch because I have no use for binary
>input.  But I assumed you told the program *somehow* that this
>was a binary data file.  How does this work at all if there isn't a
>keyword on the command line?
>

What I'm saying is if all the parameters that are controlled by the 
command line keywords are to have there own "local instance" in a 
different file, say "binfile.c" that will mean there has to be a variant 
of df_open() just for binary files, which resides inside "binfile.c". 
 It will look extremely similar to the current df_open().  I'd like to 
avoid that sort of thing, i.e., code repetition.

Dan