Re: running lua in metafun and in ConTeXt

[Jeong Dal <haksan@me.com>]

Dear Hans,

Thank you for your nice code.
lua.MP.Whatever is something!

Have a nice weekend.

Best regards,

Dalyoung

> 2020. 4. 12. 오전 2:08, Hans Hagen <j.hagen@xs4all.nl> 작성:
> 
> On 4/11/2020 4:15 PM, Jeong Dal wrote:
>> Dear all,
>> The problem is solved by using the namespace of lua as below:
>> I am not sure what I did is the right way.
>> If it is not the right way, please let me know.
>> Thanks for reading.
>> Best regards,
>> Dalyoung
>> \startluacode
>> P={}
>> combi = P
>> function P.fact (n)
>> if n <= 0 then
>> return 1
>> else
>> return n * P.fact(n-1)
>> end
>> end
>> function P.ncr(n,r)
>> return P.fact(n)/(P.fact(r)*P.fact(n-r))
>> end
>> combi = {
>> fact = fact,
>> ncr = ncr,
>> }
>> \stopluacode
>> \startbuffer[fig121]
>> numeric n,r,s,u,dx,dy,tt; u := 1.8cm;
>> path p, q;
>> pair A,B,start,now;
>> A := dir(210)*u;
>> B := dir(-30)*u;
>> dy := sind(30)*u;
>> dx := 2*cosd(30)*u;
>> for n=0 upto 4:
>> start := n*dir(210)*u;
>> for r=0 upto n:
>> s := n-r;
>> % tt := lua("mp.print(P.fact(" & decimal n & ")/(P.fact(" & decimal r & ")*P.fact(" & decimal s &" )))");
>> tt := lua("mp.print(P.ncr(" & decimal n & "," & decimal r & " ))");
>> now := start+r*right*dx;
>> dotlabel.top(textext("$\displaystyle {" & decimal n & "\choose" & decimal r & "} = "& decimal tt & "$"),now);
>> draw now -- (now+A);
>> draw now -- (now+B);
>> endfor;
>> endfor;
>> \stopbuffer
> Sunday afternoon educational moment (that you can wikify), four variants:
> 
> 1 : A more metafunish alternative of your example.
> 2 : The same but avoiding a temporary variable.
> 3 : Less code and clutter, the real deal.
> 4 : Idem, but permits more tuning at the TeX end.
> 
> \unexpanded\def\MyWhatever#1#2#3%
>  {$\displaystyle{#1\choose #2} = #3$}
> 
> \startluacode
> local function fact(n)
>    if n <= 0 then
>        return 1
>    else
>        return n * fact(n - 1)
>    end
> end
> 
> local function whatever(n,r)
>   return fact(n) / (fact(r) * fact(n-r))
> end
> 
> MP.WhateverA = whatever
> 
> function MP.WhateverB(n,r)
>   mp.quoted("%.0f",whatever(n,r))
> end
> 
> function MP.WhateverC(n,r)
>   mp.quoted([[$\displaystyle{%.0f\choose %.0f} = %.0f$]],n,r,whatever(n,r))
> end
> 
> function MP.WhateverD(n,r)
>   mp.quoted([[\MyWhatever{%.0f}{%.0f}{%.0f}]],n,r,whatever(n,r))
> end
> \stopluacode
> 
> \startbuffer[fig121]
>    numeric n, r, s, u, dx, dy, tt;
>    path p, q ; pair A, B, start, now;
>    u := 1.8cm;
>    A := dir(210)*u;
>    B := dir(-30)*u;
>    dy := sind(30)*u;
>    dx := 2*cosd(30)*u;
>    for n = 0 upto 4:
>        start := n*dir(210)*u;
>        for r = 0 upto n:
>            s := n - r;
>            now := start + r*right*dx;
>            draw (now + A) -- now -- (now + B);
> 
>            tt := lua.MP.WhateverA(n,r) ;
> 
>            dotlabel.top(textext("$\displaystyle {" & decimal n & "\choose" & decimal r & "} = "& decimal tt & "$"),now);
> 
>            dotlabel.top(textext("$\displaystyle {" & decimal n & "\choose" & decimal r & "} = "& lua.MP.WhateverB(n,r) & "$"),now);
> 
>            dotlabel.top(textext(lua.MP.WhateverC(n,r)),now);
> 
>            dotlabel.top(textext(lua.MP.WhateverD(n,r)),now);
> 
>        endfor;
>    endfor;
> \stopbuffer
> 
> \starttext
> 
>    {\switchtobodyfont[11pt]\processMPbuffer[fig121]}
> 
> \stoptext
> 
> 
> 
> -----------------------------------------------------------------
>                                          Hans Hagen | PRAGMA ADE
>              Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
>       tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
> -----------------------------------------------------------------

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