Re: [NTG-context] metafun: error when I call the same function twice consecutively.
Dear Alan,
Thank you for the clear explanation about z.
I tought that z is a special variable different from other pairs.
Now, I know that it is an equation.
Thank you again.
Best regards,
Dalyoung
> 2018. 6. 1. 오후 11:24, Alan Braslau 작성:
>
> On Fri, 01 Jun 2018 20:29:41 +0900
> Jeong Dal wrote:
>
>> After inserting a line “save x, y;”, it works.
>
> This is also defined as "clearxy ;"
>
> For those learning MetaPost, simplifying, z is defined as "(x,y)" so
> one can write
> z = (a,b) ;
> This is an EQUATION in MetaPost
> (x,y) = (a,b) ;
> not an assignment (as in most other languages), actually a pair of
> equations:
> x = a ; y = b ;
> When x and y are unknown, this can be "solved". When x and y contain
> values, it leads to "inconsistent equations".
>
> One *cannot* write
> z =: (a,b) ;
> ("=:" is the assignment operator),
> for z is just a macro, not a "pair" object or variable.
>
> This can be *very* confusing when learning MetaPost.
>
> Alan
>
> P.S.
> for i=0 upto n:
> z[i] = (i,0) ;
> endfor
> works as each element of the (pseudo)array z is unknown, at least the
> first time that it is used.
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Re: [NTG-context] metafun: error when I call the same function twice consecutively.
On Fri, 01 Jun 2018 20:29:41 +0900
Jeong Dal wrote:
> After inserting a line “save x, y;”, it works.
This is also defined as "clearxy ;"
For those learning MetaPost, simplifying, z is defined as "(x,y)" so
one can write
z = (a,b) ;
This is an EQUATION in MetaPost
(x,y) = (a,b) ;
not an assignment (as in most other languages), actually a pair of
equations:
x = a ; y = b ;
When x and y are unknown, this can be "solved". When x and y contain
values, it leads to "inconsistent equations".
One *cannot* write
z =: (a,b) ;
("=:" is the assignment operator),
for z is just a macro, not a "pair" object or variable.
This can be *very* confusing when learning MetaPost.
Alan
P.S.
for i=0 upto n:
z[i] = (i,0) ;
endfor
works as each element of the (pseudo)array z is unknown, at least the
first time that it is used.
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Re: [NTG-context] metafun: error when I call the same function twice consecutively.
Dear Henri Menke, Thank you for the solution. After inserting a line “save x, y;”, it works. Thank you so much. Best regards, Dalyoung ___ 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 webpage : http://www.pragma-ade.nl / http://context.aanhet.net archive : https://bitbucket.org/phg/context-mirror/commits/ wiki : http://contextgarden.net ___
Re: [NTG-context] metafun: error when I call the same function twice consecutively.
On 01/06/18 14:22, Jeong Dal wrote: Hi, I defined a function using MetaFun, and call it to draw a figure. It is OK when I call it once. But there is an error when it runs the same function second time. (it stops when it call fap(3,2) after fap(2,2)) I have no idea what is wrong and how to fix it. Would you please tell me what I miss? You have to save x, y; otherwise z[i] = ... will be an ill-defined equation. \startMPpage numeric u; u := 1cm; path p[]; def fap(expr n, m) = begingroup ; save x, y ; numeric size ; size := m*u ; for i = 0 upto (n*n-1): z[i] = ((i mod n),(floor(i/n)))*size; drawdot z[i] withpen pencircle scaled 5pt withcolor blue; endfor ; endgroup ; enddef; fap(2,2); fap(3,2); \stopMPpage Thank you. Best regards, Dalyoung %%% \startbuffer[test] numeric u; u := 1cm; path p[]; def fap(expr n, m) = numeric size; size := m*u; for i = 0 upto (n*n-1): z[i] = ((i mod n),(floor(i/n)))*size; drawdot z[i] withpen pencircle scaled 5pt withcolor blue; endfor; enddef; fap(2,2); fap(3,2); \stopbuffer \starttext \processMPbuffer[test] \stoptext ___ 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 webpage : http://www.pragma-ade.nl / http://context.aanhet.net archive : https://bitbucket.org/phg/context-mirror/commits/ wiki : http://contextgarden.net ___ ___ 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 webpage : http://www.pragma-ade.nl / http://context.aanhet.net archive : https://bitbucket.org/phg/context-mirror/commits/ wiki : http://contextgarden.net ___
[NTG-context] metafun: error when I call the same function twice consecutively.
Hi, I defined a function using MetaFun, and call it to draw a figure. It is OK when I call it once. But there is an error when it runs the same function second time. (it stops when it call fap(3,2) after fap(2,2)) I have no idea what is wrong and how to fix it. Would you please tell me what I miss? Thank you. Best regards, Dalyoung %%% \startbuffer[test] numeric u; u := 1cm; path p[]; def fap(expr n, m) = numeric size; size := m*u; for i = 0 upto (n*n-1): z[i] = ((i mod n),(floor(i/n)))*size; drawdot z[i] withpen pencircle scaled 5pt withcolor blue; endfor; enddef; fap(2,2); fap(3,2); \stopbuffer \starttext \processMPbuffer[test] \stoptext ___ 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 webpage : http://www.pragma-ade.nl / http://context.aanhet.net archive : https://bitbucket.org/phg/context-mirror/commits/ wiki : http://contextgarden.net ___
