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Posted to user@poi.apache.org by kix <g....@gmx.net> on 2007/08/24 08:55:32 UTC
HSSF FormulaParser / HSSFFormulaEvaluator question
Hi,
I was just wondering about the formula evaluation algorithm. Why do you need
the FormulaParser at all. The cell already contains the Ptgs within the
formula record. But you transform the Ptgs into a string representation and
then parse the string to reconstruct the Ptgs.
Maybe I miss something, but I really don't see the point.
Thx,
Günter
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Re: HSSF FormulaParser / HSSFFormulaEvaluator question
Posted by kix <g....@gmx.net>.
thx for your answer, but I wanted to adress another issue. Let me explain it
again:
To get the (calculated) value of a cell I do sth like this:
HSSFFormulaEvaluator evaluator = new HSSFFormulaEvaluator(s, workbook);
HSSFCell cell = row.getCell(colnum); //row has the type HSSFRow
At this time the cell object has already a FormulaRecord object containing
all the Ptg objects (field_8_paresed_expr)
HSSFFormulaEvaluator.CellValue actualValue = evaluator.evaluate(cell);
Now the HSSFFormulaEvaluator creates a FormulaParser with the String
representation of the formula (srcCell.getCellFormula()). getCellFormula()
converts the Ptg objects into a String (e.g. "ABS(B7)")
Now FormulaParser.parse() is called and this method parses the String and
creates again the Ptg objects - which were already known before. Afterwards
HSSFFormulaEvaluator uses the Ptg array to evaluate the formula.
Now the question: why is the String transformation necessary at all? Isn't
it possible to use the cell's Ptg objects directly?
Regards,
Guenter
Tahir Akhtar wrote:
>
> As far as I understand, the Formula Evaluator was added for the
> use-cases where a POI user wants to calculate the value of a formula in
> a cell within his Java program. The ability to parse and evaluate a
> formula is not required to simply write out excel files through POI.
> I haven't seen the internals but I guess the Ptgs you see within the
> cell object must have been generated by the Formular Parser. I think
> these Ptgs will not participate in generating actual excel file and are
> for use with Formula Evaluator only.
>
> kix wrote:
>> Hi,
>> I was just wondering about the formula evaluation algorithm. Why do you
>> need
>> the FormulaParser at all. The cell already contains the Ptgs within the
>> formula record. But you transform the Ptgs into a string representation
>> and
>> then parse the string to reconstruct the Ptgs.
>>
>> Maybe I miss something, but I really don't see the point.
>>
>> Thx,
>> Günter
>>
>
>
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Re: HSSF FormulaParser / HSSFFormulaEvaluator question
Posted by Tahir Akhtar <ta...@spectrum-tech.com>.
As far as I understand, the Formula Evaluator was added for the
use-cases where a POI user wants to calculate the value of a formula in
a cell within his Java program. The ability to parse and evaluate a
formula is not required to simply write out excel files through POI.
I haven't seen the internals but I guess the Ptgs you see within the
cell object must have been generated by the Formular Parser. I think
these Ptgs will not participate in generating actual excel file and are
for use with Formula Evaluator only.
kix wrote:
> Hi,
> I was just wondering about the formula evaluation algorithm. Why do you need
> the FormulaParser at all. The cell already contains the Ptgs within the
> formula record. But you transform the Ptgs into a string representation and
> then parse the string to reconstruct the Ptgs.
>
> Maybe I miss something, but I really don't see the point.
>
> Thx,
> Günter
>
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