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List:       koffice-devel
Subject:    Re: KSpread formulas
From:       Ariya Hidayat <ariya () tf ! itb ! ac ! id>
Date:       2002-05-20 10:31:46
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> KoScript is a programming language, therefore it interprets '&' as bitwise AND
> operation. It would be possible to make it concattenate strings when it gets
> String types passed. The question is whether this confuses the users... e.g.
> 1 & 3 results in 3,
> Hello & World gets HelloWorld

Which is exactly why I propose to strip more parts of KoScript. Evaluating
expression in spreadsheet app like KSpread should be not as complex as
executing script commands. Things like "1 & 3" won't likely appear in
KSpread expression anyway. And making KoScript somehow understand the
so-called Shared Formula in Excel would be another The Right Thing.

If nobody against that, furthermore I'd like to propose the following
points. I have digged through Gnumeric source code and realized that there
are couple of good things we can adopt.

(1) making a cell value stored in KSpreadValue class. KSpreadCell is quite
a mess with value handling and so on. and we don't need integer, all
number are just numbers (should be double), including date/time. this
value can holds error from evaluating the expression, incl. error code and
optionally message. when we move to rich-text (KoTextParag), it should be
easy to extend this class.

(2) define 'format', i.e how the cell value should be displayed, e.g
precision, currency, and so on. should be put in class KSpreadFormat. and
this is likely to be shared among. cells will "apply" a prefined/custom
format. improving cell formatting with Excel would be possible. OTOH it
also reduces KSpreadCell again.

(3) define 'layout', which somehow already there (KSpreadLayout). layout
defines apperance of the cell, e.g border, color, font, etc. think of
value vs format+layout like document vs view.

(4) if we have (2) and (3), it should be difficult to have 'style'.

(5) define 'expression' (class KSpreadExpression) will be used to parse
and evaluate formula/expression.  again, it can be shared among cells for
good (copy formula from one cell to another(s) and you only have one
instance of KSpreadExpression). for starting, KSpreadExpression might be
simply a wrapper/adapter for KSInterpreter.  when we move on, it might be
interesting to parse expression once and stored in Polish notation (ala
Lotus 1-2-3), then with a simple stack-machine, executing expression
should be faster. add GNU MP library and KSpread becomes the most precise
spreadsheet ever :-) its lexical analyzer is also useful to create
color-syntax-highlighted formula editor.

Ideas ? Comments ? Flames ?

Regards,

Ariya



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