Re: Filter input/parsing timing

[Nathan Bell]

Thanks for the advice. Just for posterity, I had to create by barcode 
function as such:

def @Barcode
named @H {.75i}
named @W {2i}
right x
{
   def @BarCode
   left y
   right x
   {
       def @Filter {"wbar -b \"" y "\"" > @FilterOut}
       {lines @Break x}
   }
   {x @BarCode {}} @Graphic { @W @Wide //@H }
}

where wbar is the external application to create a barcode. It's called 
as such:

@Barcode @W {2.5i} @H {.375i} {barcode to encode}

If anyone wants the Tcl / C application I use (or a pure C application) 
to create the barcodes, give me a holler and I'll hook you up.

Jeff Kingston wrote:
> Although the right parameter of a filtered symbol goes directly from
> the input file into the filter with no possibility of variable
> substitution first, the filter command itself does go through
> Lout variable substitution.  So you need to move your filter
> input from stdin to a command line option, like this:
>
> def @BarCode
>   left product_code
>   right junk
> {
>   def @Filter { "product_code_to_barcode -c \"" product_code "\"" }
> }
>
> This way, when you call
>
>     17830-363 @BarCode {}
>
> you will be executing your filter as
>
>     product_code_to_barcode -c "17830-363"
>
> It will be fed an empty stdin file, or rather a file with just
> a newline in it, the result of passing the contents of {}
> uninterpreted to the filter.  You don't have to read that file.
>
> If I've understood you correctly, the output of your filter is
> text of the form
>
>    { ... } @Graphic { ... }
>
> This Lout object will then be the value of 17830-363 @BarCode {}
> as desired.  It sounds like you have the best (most flexible) plan
> for getting the size right, so no need to change anything there.
>
> Jeff
>