[Kst] Re: branches/work/kst/portto4/kst/src/datasources/ascii

[Peter Kümmel]

On 24.01.2011 17:30, Brisset, Nicolas wrote:
>> Fixed-width columns are optimized, column width == 5
>>  1234 1234 1234 1234;
>> -1234-1234 1234 1234;
>> -1234 1234 1234 1234;
>> +1234 1234-1234-1234;
>>
>> but we could also optimize for different column width are constant:
>>  1234; 123456789; 12; 1234444;
>>  1234;-123456789; 12;+1234444;
>>
>> only the place of the ; has to be the same in each row.
>>
>> And I've seen no problems when the number string starts with a
> whitespace.
> OK, here are a couple of questions to be able to improve the GUI, which
> is a bit broken/hard to figure out currently.
> 
> So if I understand it correctly, when all columns don't have the same
> width but each still has a constant width, then we can perform a
> specific optimization. Is that correct? 

Yes, this was the initial idea.

> 
> Can we optimize more if all columns have the same width than if each has
> a constant width?

Isn't this the already available option.

> 
> And another important question: can you compute the width of each column
> reliably when they are delimited by whitespace, or does it need a custom
> delimiter? Finding out the width with whitespace sounds tricky, because
> you could have a sign coming only after a large number of samples, and
> we can't parse the whole file to determine which optimization is
> applicable!

To find the column start I use the old algorithm but stop when I've find
it an remember the position. So when we search for whitespace I don't see
a problem, for instance, when we are looking for column 2

1234 -88888
1234  99999

it would always use the first space after 1234.


> Or do we have a simple criterion such as: the first whitespace char
> after the numbers in a given column are always aligned?

OK, now I understand:

1234             8888888
1234567898       9999999


this would not work. The numbers must be aligned to the right.

> 
> Depending on your answers, I think we have to change the GUI (and
> unfortunately the code and possibly storage format in the .kst) a bit. 
> 
> Nicolas
> 
> P.S.: since we're doing so much work on the ASCII datasource, I think
> I'll end up adding units as well for 2.0.3. 

OK, why not.

> 
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