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. ___________________________________________________________________________________ If your question is of interest to others as well, please add an entry to the Wiki! maillist : email@example.com / 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 ___________________________________________________________________________________