Re: [Chicken-users] format-modular feature request: defining one's own multi-part formats

[Kon Lovett]

On Mar 7, 2008, at 9:08 AM, Robin Lee Powell wrote:

> I'd like to define my own %[...%] sort of formatter using
> format-modular, but it seems to be impossible without copying most
> of the egg into my own code!  Could this be added as a general
> feature?

No quite sure what you mean. Is '%' to be the escape character,  
instead of '~'? This is possible but you would need to override the  
"*formatter-cond*" to provide new semantics. And all format codes  
would need to use '%' as the escape.

Or are you asking for a user defined multi-character escape+code  
sequence that would coexist with the default escape+code sequences? I  
suppose this could be done but would require some surgery.

For now the recommended method is to pick some unused escape sequence  
and define your own formatter function. These are reserved: ?!{}^()%/ 
~|_[;]*$&<>IASCRFEQGTYPXDOBK@:V#',+-0123456789
but `.HJLMNUWZ are available.

Unfortunately there wasn't an exported procedure to acquire an  
argument - this has been fixed with the '*formatter-next-argument'  
procedure in the 1.8 release/3.

(define (formatter-mine state start params colon atsign)
  (let-optionals params ((foo 1) (bar #f)) ; these are the parsed  
parameter values, ex.
    (let ((obj (*formatter-next-argument state)))
      (*formatter-out-string state (with-foobar obj foo bar)) ) ) )

(define *my-formatter* `((#\Z ,(formatter-function formatter-mine))))

(define extd-format (make-format-function #f #\~ (cons *my-formatter*  
*formatter-cl*)))

> Thanks.
>
> -Robin
>
> --
> Lojban Reason #17: http://en.wikipedia.org/wiki/Buffalo_buffalo
> Proud Supporter of the Singularity Institute - http://singinst.org/
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>
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Best Wishes,
Kon