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Re: [css3-values] New WD for Values & Units

From: Kornel Lesinski <kornel@ldreams.net>
Date: Fri, 29 Jul 2005 20:40:23 +0000
Message-ID: <op.suozm4pi602458@osx.local>
To: www-style@w3.org




On Fri, 29 Jul 2005 18:08:57 +0100, Christoph P├Ąper  
<christoph.paeper@tu-clausthal.de> wrote:

> 3.7.4. The 'calc' function
>
>    Should we introduce mathematical expressions to calculate values?
>
> I think the majority of webdesigners would say yes. I'm undecided. I'm  
> also not sure whether a generic 'calc()' or distinctive 'add()',  
> 'sub()', 'mul()', 'div()', 'mod()', 'pow()' etc. functions were  
> preferable.

I've implemented server-side CSS preprocessor and written few stylesheets  
using math expressions and constants.

My suggestion for syntax is: shortest possible. calc() seems too much to  
write.  sub() might avoid confusion with minus and hyphenated identifiers,  
but again - it's too verbose.

I suggest new syntax - expressions to be just in parentheses.

  foo {width: (2px + 2em);}

This is compatible with CSS parsing rules and does not conflict with any  
current syntax.

Formally it'd be (basing on CSS2.1 grammar appendix):

term
   : unary_operator?
     [ NUMBER S* | PERCENTAGE S* | LENGTH S* | EMS S* | EXS S* | ANGLE S* |
       TIME S* | FREQ S* | function ]
   | STRING S* | IDENT S* | URI S* | UNICODERANGE S* | hexcolor |

   "(" S* term S* [ math_operator S* term S* ]* ")" S*   /* added  
mathematical expressions */
   ;


-- 
regards, Kornel Lesinski
Received on Monday, 1 August 2005 10:09:12 GMT

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