Thomas A. Schmitz wrote:
> Hi all,
>
> cleaning up the code in my module, I run into a very interesting
> problem. I want to pass a user-defined value to Metapost. Until now,
> the value "scale" had to be numeric, and I used it like this:
>
> draw fullcircle scaled \MPvar{scale}mm
>
> and Metapost was happy, and I was too. Now Aditya made the reasonable
> suggestion that users should be allowed to input any dimension and not
> be restricted to "mm." Easy enough. However, I also want a fallback
> just in case they input a number, in that case, I want to fall back to
> mm as a default. So I tried (after Taco's excellent explanation on the
> wiki):
>
> \expandafter\processaction\expandafter[\CVERscale]%
> [\v!unknown=>{\doifdimensionelse%
> {\CVERscale}%
> {\setupMPvariables[CircleSomething][scale=\CVERscale]}%
> {\doifnumberelse%
> {\CVERscale}%
> {\newdimen\CIscale \global\CIscale=\CVERscale mm
> {\setupMPvariables[CircleSomething][scale=\the\CIscale]}}%
> {\setupMPvariables[CircleSomething][scale=10mm\relax]%
> \message{Please give a proper value for the "scale"
> argument!}}}},
> \v!default=>{\setupMPvariables[CircleSomething][scale=10mm
> \relax]}]
>
>
> So what I want: first check if \CVERscale is a dimension; if it is,
> assign it to the "scale" parameter. If it isn't, check if it is a
> number; if this is the case, append the unit "mm" to it and put it
> into a dimension register. If it isn't a number either, make the value
> sufficiently absurd for the user to realize and write a message to the
> terminal. This is all fine and dandy and works, sort of: it works
> perfectly with dimensions, but when I try with a number as input, it
> doesn't fall back to the unit "mm," but to "pt," AFAICS. That's nice
> too, but I have no clue why, and I would prefer mm. If it helps, I can
> try to give you a minimal test file tomorrow, but maybe somebody spots
> what I'm doing wrong? (I tried both with mkii and mkiv, and always get
> the same result.)
\startluacode
document.mymodule = document.mymodule or { }
function document.mymodule.checkdimen(str)
return (str:find("%a%a$") and str) or (str .. "mm")
end
\stopluacode
\ctxlua{document.mymodule.checkdimen("#1")}
or more fancy:
function document.mymodule.checkdimen(str)
if not str:find("%a%a$") then
str = str .. "mm"
ctx.writestatus("mymodule","you forgot a dimension unit, so I
made it up for you: %s",str)
end
return str
end
for mkii you can use \doifdimensionelse (it reminds me to implement that
in mkiv)
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