RE: [Groff] string variable in pic

[Ted Harding]

On 11-Dec-05 Heinz-Jürgen Oertel wrote:
> 
> Hello,
> I'm searching for a way to put strings in pic variable,
> but found no way doing it.
> What I like to do  is something like:
> 
> .PS
> bcolor = "red"
> 
> define cbox {
>     box wid $1 color bcolor
> }
> .PE
> 
> .PS
> cbox(1) "this is red"
> bcolor "yellow"
> cbox(1) "this is yellow"
> .PE

I *think* (but am not absolutely sure) that the reason your
approach does not work is that the assignment "=" has the syntax

  variable = expression

and, as far as I can tell, "expression" in pic can only be numeric
(or logical), so that there is no such thing as a string-valued
expression (or variable). More generally, a string (either quoted
literally or as returned by 'sprintf') is an object, like 'box'.

However, it is possible to do what you want by macro substitution:

.PS
define cbox {
    box wid $1 color $2
}
.PE

.PS
bcolor="red"
cbox(1,"red") "this is red"
cbox(1,"yellow") "this is yellow"
.PE

This does not evaluate any expressions: When (e.g.) "red" is
encountered in 'cbox(1,"red")' it is substituted for $2 in
the definition of 'cbox', i.e. it effectively re-writes 'cbox'.

Hoping this helps!
Ted.


> 
> Another interesting feature would be if 
> \n[.M] could return the numerical values of the color components.
> In this case one could define a new color which is sometimes darker or
> more 
> bright, or "more red" etc. This can be used to produce shaded colored
> boxes 
> in pic.
> 
> Hope I get help
>  Regards
>   Heinz
>  
> 
> 
> _______________________________________________
> Groff mailing list
> address@hidden
> http://lists.gnu.org/mailman/listinfo/groff

--------------------------------------------------------------------
E-Mail: (Ted Harding) <address@hidden>
Fax-to-email: +44 (0)870 094 0861
Date: 11-Dec-05                                       Time: 14:02:36
------------------------------ XFMail ------------------------------