When I have a Lua function with 2 arguments: \startluacode function f(a,b) ... \stopluacode called through: \def\callf#1#2{\ctxlua{f("#1","#2")}} and do this actually with one argument: \callf{one} then I find that the absent argument b in f(a,b) is not nil but a string of length 1. That is a bit of a nuisance because I would like to use the Lua idiom: function f(a,b) local b = b or default but that is frustrated by the behaviour shown. Is this an artifact of either luatex or ConTeXt? Can it be avoided such that in this case b will be nil? Hans van der Meer
On 30-3-2010 19:45, Hans van der Meer wrote:
When I have a Lua function with 2 arguments: \startluacode function f(a,b) ... \stopluacode
called through: \def\callf#1#2{\ctxlua{f("#1","#2")}}
and do this actually with one argument: \callf{one}
so, #1 will be one and #2 will be the next token (whatever that is)
then I find that the absent argument b in f(a,b) is not nil but a string of length 1.
That is a bit of a nuisance because I would like to use the Lua idiom: function f(a,b) local b = b or default but that is frustrated by the behaviour shown.
Is this an artifact of either luatex or ConTeXt? Can it be avoided such that in this case b will be nil?
just tex but in any case even if #2 is empty you need to test like this local b = b ~= "" and b or default watch the order ... we want b to be set to b when not empty Hans ----------------------------------------------------------------- Hans Hagen | PRAGMA ADE Ridderstraat 27 | 8061 GH Hasselt | The Netherlands tel: 038 477 53 69 | fax: 038 477 53 74 | www.pragma-ade.com | www.pragma-pod.nl -----------------------------------------------------------------
On Tue, Mar 30 2010, Hans van der Meer wrote:
called through: \def\callf#1#2{\ctxlua{f("#1","#2")}}
and do this actually with one argument: \callf{one}
then I find that the absent argument b in f(a,b) is not nil but a string of length 1.
Hello Hans, You want probably something like this: \startluacode userdata = userdata or {} function userdata.f(a, b) b = b or "default value" tex.print(string.format("a = '%s' and b = '%s'\\par", a, b)) end \stopluacode \def\callf{\dodoubleempty\docallf} \def\docallf[#1][#2]{\ctxlua{userdata.f("#1"\ifsecondargument, "#2"\fi)}} \starttext \callf[one] \callf[one][two] \callf[one][] \callf[][] \callf[][two] \callf[] \stoptext Cheers, Peter -- Contact information: http://pmrb.free.fr/contact/
participants (3)
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Hans Hagen -
Hans van der Meer -
Peter Münster