arguments to ctxlua

arguments to ctxlua

[Hans van der Meer]

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

[Hans Hagen]

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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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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___________________________________________________________________________________

Re: arguments to ctxlua

[Peter Münster]

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/


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maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
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