Re: [NTG-context] ! Declared variable conflicts with previous vardef [Metapost]

[Taco Hoekwater]

Hi,



> On 3 Jan 2019, at 11:31, Fabrice Couvreur  wrote:
> 
> Hi,
> It is true that Alan has already answered this question but I was misled 
> because the file that I compiled without problem is this one, even leaving 
> pair z[ ] (I can think that it is because of this instruction   z := point 
> 3.6 of p ;)

It works because of the "pair z” statement. Attempted explanation:


Metapost variable names are built up hierarchically. When you
say “path p” or “color V.Q” or “numeric z[]” or “vardef z”, it 
changes the type of just the last segment, not other segments
(not even the immediately preceding one).

Note that in the case of z[], the last variable segment is the 
common subscript [] not the ‘alphabetical segment’ “z”. 

It is actually OK to say e,g, 

pair z ; 
color z[];
numeric z[].a;
z := point 3.6 of p ;
z[1] := red;
path z[]; % z[1] is now undefined again after this line,
  % but z[].a is still numeric
z[3] = unitsquare;
z[2].a = 5;

Redeclaration of intermediate segments works for all declarations except 
for ‘vardef’. The reason behind this is that vardefs can have suffixes, 
and metapost does not really differentiate between vardefs defined with
and without suffixes (except when called). Of course actual suffixes 
would interfere with the parsing of any potentially following name 
segments, which is why re-declarations ‘below’ a vardef’d segment are 
illegal.

I hope that makes sense, it is not the easiest thing to explain.

Best wishes,
Taco 


> 
> \starttext
> \startMPpage[offset=2pt]
>  path p, q, r, b ; pair z ;
>  p := unitsquare scaled 4cm ;
>  z := point 3.6 of p ;
>  q := z--urcorner p ;
>  r := z--urcorner p-- reverse bottomboundary p--cycle ;
>  b := reverse bottomboundary p ; 
>  %r := q -- reverse bottomboundary p -- cycle ; definition of Hans
>  draw b--q withpen pencircle scaled 1mm withcolor red ;
>  draw p ;
>  draw r numberstriped (.25,10,5) withcolor magenta ;
>  label.llft("B", p) ;
>  label.lrt("C", p) ;
>  label.ulft("A", p) ;
>  label.urt("D", p) ;
>  label.lft("M", p) ;
> \stopMPpage
> \startMPpage[offset=2pt]
>   defaultfont := "texgyrepagella-regular*default" ;
>   defaultscale :=0.8 ;
>   path p, q, r, b ; pair z[];
>   p  := unitsquare xyscaled (9cm,5cm) ;
>   z[0] = (2cm,0cm) ;
>   z[1] = (2cm,2cm) ;
>   z[2] = (0cm,2cm) ;
>   q := llcorner p--z[0]--z[1]--z[2]--cycle ;
>   r := unitsquare xyscaled (7cm,3cm) shifted(2cm,2cm) ;
>   b := z[2]--z[1]--ulcorner r--urcorner p--lrcorner r--z[1]--z[0]--llcorner 
> p--cycle ;
>   draw p ;
>   draw b numberstriped (.25,15,5) withcolor magenta ;
>   label.llft("A", p) ;
>   label.lrt("D", p) ;
>   label.ulft("C", p) ;
>   label.urt("B", p) ;
>   label.lft("M", z[2]) ;
>   label.ulft("N", z[1]) ;
>   label.bot("P", z[0]) ;
>   label.top("J", ulcorner r) ;
>   label.rt("I", lrcorner r) ;
>   label.bot(btex $x$ etex,(llcorner p+z[0])/2);
>   label.lft(btex $x$ etex,(llcorner p+z[2])/2);
> \stopMPpage
>
> \stoptext
> 
> Le jeu. 3 janv. 2019 à 07:12, Alan Braslau  a écrit 
> :
> On Thu, 3 Jan 2019 16:22:06 +1300 (UTC)
> Henri Menke  wrote:
> 
> > z is a MetaPost intrinsic, something along the lines of
> > 
> > vardef z@#=(x@#,y@#) enddef;
> > 
> > so you can't use the same name for a pair.  Actually you can simply
> > delete the declaration
> > 
> >pair z[];
> 
> I had already told Fabrice this a couple of days ago...
> 
> Alan
> ___
> 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
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> ___
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> Wiki!
> 
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> ___

Taco Hoekwater
Elvenkind BV




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Re: [NTG-context] ! Declared variable conflicts with previous vardef [Metapost]

[Fabrice Couvreur]

Hi,
It is true that Alan has already answered this question but I was misled
because the file that I compiled without problem is this one, even leaving
pair z[ ] (I can think that it is because of this instruction   z := point
3.6 of p ;)

\starttext
\startMPpage[offset=2pt]
 path p, q, r, b ; pair z ;
 p := unitsquare scaled 4cm ;
* z := point 3.6 of p ;*
 q := z--urcorner p ;
 r := z--urcorner p-- reverse bottomboundary p--cycle ;
 b := reverse bottomboundary p ;
 %r := q -- reverse bottomboundary p -- cycle ; definition of Hans
 draw b--q withpen pencircle scaled 1mm withcolor red ;
 draw p ;
 draw r numberstriped (.25,10,5) withcolor magenta ;
 label.llft("B", p) ;
 label.lrt("C", p) ;
 label.ulft("A", p) ;
 label.urt("D", p) ;
 label.lft("M", p) ;
\stopMPpage
\startMPpage[offset=2pt]
  defaultfont := "texgyrepagella-regular*default" ;
  defaultscale :=0.8 ;
  path p, q, r, b ;* pair z[];*
  p  := unitsquare xyscaled (9cm,5cm) ;
  z[0] = (2cm,0cm) ;
  z[1] = (2cm,2cm) ;
  z[2] = (0cm,2cm) ;
  q := llcorner p--z[0]--z[1]--z[2]--cycle ;
  r := unitsquare xyscaled (7cm,3cm) shifted(2cm,2cm) ;
  b := z[2]--z[1]--ulcorner r--urcorner p--lrcorner r--z[1]--z[0]--llcorner
p--cycle ;
  draw p ;
  draw b numberstriped (.25,15,5) withcolor magenta ;
  label.llft("A", p) ;
  label.lrt("D", p) ;
  label.ulft("C", p) ;
  label.urt("B", p) ;
  label.lft("M", z[2]) ;
  label.ulft("N", z[1]) ;
  label.bot("P", z[0]) ;
  label.top("J", ulcorner r) ;
  label.rt("I", lrcorner r) ;
  label.bot(btex $x$ etex,(llcorner p+z[0])/2);
  label.lft(btex $x$ etex,(llcorner p+z[2])/2);
\stopMPpage

\stoptext

Le jeu. 3 janv. 2019 à 07:12, Alan Braslau  a
écrit :

> On Thu, 3 Jan 2019 16:22:06 +1300 (UTC)
> Henri Menke  wrote:
>
> > z is a MetaPost intrinsic, something along the lines of
> >
> > vardef z@#=(x@#,y@#) enddef;
> >
> > so you can't use the same name for a pair.  Actually you can simply
> > delete the declaration
> >
> >pair z[];
>
> I had already told Fabrice this a couple of days ago...
>
> Alan
>
> ___
> 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
>
> ___
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Re: [NTG-context] ! Declared variable conflicts with previous vardef [Metapost]

[Alan Braslau]

On Thu, 3 Jan 2019 16:22:06 +1300 (UTC)
Henri Menke  wrote:

> z is a MetaPost intrinsic, something along the lines of
> 
> vardef z@#=(x@#,y@#) enddef;
> 
> so you can't use the same name for a pair.  Actually you can simply
> delete the declaration
> 
>pair z[];

I had already told Fabrice this a couple of days ago...

Alan
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Re: [NTG-context] ! Declared variable conflicts with previous vardef [Metapost]

[Henri Menke]

z is a MetaPost intrinsic, something along the lines of

vardef z@#=(x@#,y@#) enddef;

so you can't use the same name for a pair.  Actually you can simply
delete the declaration

   pair z[];

from your file and it will work as intended.  If you insist on using
your own declaration of z, then you have to stash away MetaPost's
definition using

   save z; pair z[];

I recommend the former, just delete pair z[];

On 3/01/19 2:43 PM, Fabrice Couvreur wrote:
> Hi,
> I have a problem compiling this file.
> Thanks.
> Fabrice
> 
> ## test file 
> \starttext
> \setupbodyfont [pagella,9pt]
> \startMPpage[offset=2pt]
>   path p, q, r, b ; pair z[];
>   p  := unitsquare xyscaled (9cm,5cm) ;
>   z[0] = (2cm,0cm) ;
>   z[1] = (2cm,2cm) ;
>   z[2] = (0cm,2cm) ;
>   q := llcorner p--z[0]--z[1]--z[2]--cycle ;
>   r := unitsquare xyscaled (7cm,3cm) shifted(2cm,2cm) ;
>   b := z[2]--z[1]--ulcorner r--urcorner p--lrcorner r--z[1]--z[0]--llcorner
> p--cycle ;
>   draw p ;
>   draw b numberstriped (.25,15,5) withcolor magenta ;
>   label.llft("A", p) ;
>   label.lrt("D", p) ;
>   label.ulft("C", p) ;
>   label.urt("B", p) ;
>   label.lft("M", z[2]) ;
>   label.ulft("N", z[1]) ;
>   label.bot("P", z[0]) ;
>   label.top("J", ulcorner r) ;
>   label.rt("I", lrcorner r) ;
>   label.bot(btex $x$ etex,(llcorner p+z[0])/2);
>   label.lft(btex $x$ etex,(llcorner p+z[2])/2);
> \stopMPpage
> 
> \stoptext
> #
> ! Declared variable conflicts with previous vardef.
> 
> ;
> <*> path p, q, r, b ; pair z[] ;
> z[0] = (2cm,0cm) ; z[1] = (2cm,2cm) ; z[2] ...
> You can't use, e.g., `numeric foo[]' after `vardef foo'.
> Proceed, and I'll ignore the illegal redeclaration.
> 
> 
> ___
> If your question is of interest to others as well, please add an entry to the 
> Wiki!
> 
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> 

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[NTG-context] ! Declared variable conflicts with previous vardef [Metapost]

[Fabrice Couvreur]

Hi,
I have a problem compiling this file.
Thanks.
Fabrice

## test file 
\starttext
\setupbodyfont [pagella,9pt]
\startMPpage[offset=2pt]
  path p, q, r, b ; pair z[];
  p  := unitsquare xyscaled (9cm,5cm) ;
  z[0] = (2cm,0cm) ;
  z[1] = (2cm,2cm) ;
  z[2] = (0cm,2cm) ;
  q := llcorner p--z[0]--z[1]--z[2]--cycle ;
  r := unitsquare xyscaled (7cm,3cm) shifted(2cm,2cm) ;
  b := z[2]--z[1]--ulcorner r--urcorner p--lrcorner r--z[1]--z[0]--llcorner
p--cycle ;
  draw p ;
  draw b numberstriped (.25,15,5) withcolor magenta ;
  label.llft("A", p) ;
  label.lrt("D", p) ;
  label.ulft("C", p) ;
  label.urt("B", p) ;
  label.lft("M", z[2]) ;
  label.ulft("N", z[1]) ;
  label.bot("P", z[0]) ;
  label.top("J", ulcorner r) ;
  label.rt("I", lrcorner r) ;
  label.bot(btex $x$ etex,(llcorner p+z[0])/2);
  label.lft(btex $x$ etex,(llcorner p+z[2])/2);
\stopMPpage

\stoptext
#
! Declared variable conflicts with previous vardef.

;
<*> path p, q, r, b ; pair z[] ;
z[0] = (2cm,0cm) ; z[1] = (2cm,2cm) ; z[2] ...
You can't use, e.g., `numeric foo[]' after `vardef foo'.
Proceed, and I'll ignore the illegal redeclaration.
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