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 <braslau.l...@comcast.net> 작성:
>
> On Fri, 01 Jun 2018 20:29:41 +0900
> Jeong Dal <hak...@me.com> 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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