How to use in Metafun, a function defined in Lua

How to use in Metafun, a function defined in Lua

[Otared Kavian]

Hi all,

I would like to use a math function defined in lua in Metafun in order to draw its graph, together with the graphs of some other functions.
As a simple example consider the following:

%%% begin lua-metafun-example.tex
\startluacode 
	function document.myfunction(n,x)
		local S
		S = math.sin(n*x)
		return S
	end
\stopluacode

\starttext

Here \type{document.myfunction(n,x)} is $\sin(nx)$. For instance when $n = 2$ and $x = 355/113$ we have:

\type{document.myfunction(2,355/113)} $=\cldcontext{document.myfunction(2,355/113)} \sim 0$.

\startplacefigure[title={Nothing works\dots}]
\startMPcode{GridAxis}
	numeric gu ; gu = 5mm ; % gu = graph unit
	draw image (
	draw function (1,"x","document.myfunction(2,x)", % <-- this does not work
%	draw function (1,"x","sin(2*x)", % <-- this works
	-355/113,355/113,.01)
	scaled gu 
	withpen pencircle scaled .075pt
	withcolor darkred ;
	) xsized .7TextWidth ;
\stopMPcode
\stopplacefigure

\stoptext
%%% end lua-metafun-example.tex

Here one sees that the function « document.myfunction » is well defined in Lua and is known in ConTeXt, but I cannot use it in a Metapost code: how can one do that?

Thanks in advance for any help.
Best regards: Otared
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Re: How to use in Metafun, a function defined in Lua

[Hans Hagen]

On 12/28/2019 4:22 PM, Otared Kavian wrote:
> Hi all,
> 
> I would like to use a math function defined in lua in Metafun in order to draw its graph, together with the graphs of some other functions.
> As a simple example consider the following:
> 
> %%% begin lua-metafun-example.tex
> \startluacode
> 	function document.myfunction(n,x)
> 		local S
> 		S = math.sin(n*x)
> 		return S
> 	end
> \stopluacode
> 
> \starttext
> 
> Here \type{document.myfunction(n,x)} is $\sin(nx)$. For instance when $n = 2$ and $x = 355/113$ we have:
> 
> \type{document.myfunction(2,355/113)} $=\cldcontext{document.myfunction(2,355/113)} \sim 0$.
> 
> \startplacefigure[title={Nothing works\dots}]
> \startMPcode{GridAxis}
> 	numeric gu ; gu = 5mm ; % gu = graph unit
> 	draw image (
> 	draw function (1,"x","document.myfunction(2,x)", % <-- this does not work
> %	draw function (1,"x","sin(2*x)", % <-- this works
> 	-355/113,355/113,.01)
> 	scaled gu
> 	withpen pencircle scaled .075pt
> 	withcolor darkred ;
> 	) xsized .7TextWidth ;
> \stopMPcode
> \stopplacefigure
> 
> \stoptext
> %%% end lua-metafun-example.tex
> 
> Here one sees that the function « document.myfunction » is well defined in Lua and is known in ConTeXt, but I cannot use it in a Metapost code: how can one do that?
you confuse lua and mp functions

\startluacode
	function MP.myfunction(n,x)
		return math.sin(n*x)
	end
\stopluacode

\starttext

\startMPcode
	numeric gu ; gu = 5mm ;
     vardef myfunction(expr n, x) = MP.myfunction(n,x) enddef ;
	draw image (
         draw function (1,"x","myfunction(2,x)",-355/113,355/113,.01)
             scaled gu
             withpen pencircle scaled .075pt
             withcolor darkred ;
	) xsized .7TextWidth ;
\stopMPcode

\stoptext



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