* arguments to ctxlua
@ 2010-03-30 17:45 Hans van der Meer
2010-03-30 17:52 ` Hans Hagen
2010-03-30 18:30 ` Peter Münster
0 siblings, 2 replies; 3+ messages in thread
From: Hans van der Meer @ 2010-03-30 17:45 UTC (permalink / raw)
To: NTG ConTeXt
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
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* Re: arguments to ctxlua
2010-03-30 17:45 arguments to ctxlua Hans van der Meer
@ 2010-03-30 17:52 ` Hans Hagen
2010-03-30 18:30 ` Peter Münster
1 sibling, 0 replies; 3+ messages in thread
From: Hans Hagen @ 2010-03-30 17:52 UTC (permalink / raw)
To: mailing list for ConTeXt users
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
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: arguments to ctxlua
2010-03-30 17:45 arguments to ctxlua Hans van der Meer
2010-03-30 17:52 ` Hans Hagen
@ 2010-03-30 18:30 ` Peter Münster
1 sibling, 0 replies; 3+ messages in thread
From: Peter Münster @ 2010-03-30 18:30 UTC (permalink / raw)
To: mailing list for ConTeXt users
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/
___________________________________________________________________________________
If your question is of interest to others as well, please add an entry to the Wiki!
maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
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___________________________________________________________________________________
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